Alpha!Robby/Late Blooming Omega!Reader/Omega!Moon
(Unedited) (a/b/o, Smut, Knotting, Threesome, Omega’s First Heat) ( @gemini-sensei )
•Originally Moon and Robby were the first ones dating each other. It was the start of senior year and everything was new to them. Between them being in their final year of high school and being together for about two years. It was kinda blissful for the two mates. A lot of people still couldn't believe they even got together, believing they were too far apart life-wise. But they were extremely wrong. Both parties are actually pretty similar and have a lot in common. They complement each other perfectly.
•Moon loves the fact that Robby is mostly down to earth and Robby loves the fact Moon is all about the earth. Both of them strive to be better and do good. Even though they come from different backgrounds they still understand each other. Moon pushes Robby to be the best just as Robby does it back to her. Pushing each other to thrive. Moon helped him with school work and he helped her with after-school activities. 
•At school they are the basic alpha and omega couple. Moon is sweet and kind, making sure to cuddle and love on Robby as much as she can without getting pda detention. Robby does the same as he scents her every time she is near him. He hugs her and scents her up as much as he can. They cling to each other softly and nonchalantly. Small peaks when in the public view, but also hot make-outs in private corners of the school. Lots of tiny laughs mixed with soft kisses.
•For a long time that is how their relationship went. It was blissful and never got bored. That senior year changed their bond, for the good. Early into the school year is when things slowly started to shift. That is when they first meet the cute and shy introverted Reader. It was all by accident when they met her.
• They were walking in the hall together holding hands. Moon was telling Robby about a project she was doing for one of her classes and how she might need some help with it. Robby was paying attention to her more than what was going on around them at that moment. They only stopped in their tracts when a loud bang filled the hall way making them and a few others look towards where the sound came from. Robby out of instinct pulled Moon to his chest. They watched as some jock alphas pushed the chubby girl into a locker. Laughing as she winced in pain after being slammed into the hard metal.
“That's what you get, your a fucking senior and you haven't even presented. Just say you're a beta at this point.”
Those were just a few insults they heard as the jocks passed them.
•Moon was the first one to wall over and ask if the chubby girl was ok. The couple was sure she was new by the fact that they had never seen her bed. Not in class or even in passing. Robby walked over a minute later and was a little shocked. He tried his best to hide his own shock as he sniffed the air. There was nothing, no scent or anything connected to the girl. Most alphas like himself had a thick strong scent while omegas has more soft and potent scents, betas had a slight scent but nothing like the other two. This girl had nothing. She clearly never presented which was basically unheard of these days.
•Moon was quick to introduce both of them. Robby gave a small wave at the very embarrassed girl but she still gave a small smile back. The three talked for a few minutes before the next bell rang. They found out they were right and that she was new, her name was Reader and she had just transferred to West-valley. She was a senior like them as well. Moon was happy to look at her schedule and point out a class or two that they were apparently in together, one or two she was in with Robby. They were happy to show her around and even walk her to class.
•Within a few weeks, they could call each other friends. The couple grew to like being around the chubby girl more and more as time went on. Once they broke through her thick wall of shyness she was adorable. She followed them around almost like a puppy. Unlike some of their other friends, she never had anything bad to say about their relationship. She actually at one point said that they went together extremely well. Like they were made for each other. Moon was so excited when she said that and of course hugged the girl tightly. Reader got a little flustered as the kind girl squeezed her. Robby just sat by laughing.
• They didn't realize how close they were getting to Reader until people pointed it out. Sam and Yasmine told Moon that she was kinda hanging out with both Reader and Robby more than just hanging out with her alpha, Robby. Moon had never thought about it before. Miguel and Hawk where quick to say something about the fact that he was scenting Reader just as much as he did Moon. Which they thought was weird seeing Reader...wasn't anything. She wasn't a alpha or omega, she wasn't even a beta. She didn't even need to be scented. He didn't know why but he growled at them. Deep down he didn't like the way they said that about Reader.
•Months passed and they grew even stronger as three. Between school and their personal lives they got even closer. If Robby wasn't with the boys or Moon he was with Reader. If Moon wasn't with Robby or the girls she was out with Reader. The three of them almost grew inseparable as time passed. Over time they learned more about each other, in and out. The pair was shocked once again when they finally got the full story about what was going on with Reader biological. She was embarrassed to talk about it for fear that they wouldn't like her anymore. they of course made the biggest effort to show that wasn’t the case and that they wouldn’t care. They liked her for her not what her biology said.
• She explained that she thought hitting puberty would cause her to present in middle school like everybody else. Then puberty hit and she never presented in middle school. She felt like she was a borderline freak by the time she was in high school because she still hadn't presented. By sophomore year she had gone to a doctor and they had no answers for her. Now she was a senior with still no signs of her presenting any time soon. She didn't care what she ended up being, she just wished it would happen soon so she could know. The omega and alpha felt for her as she sobbed out her story and feelings. They hugged her and scented her, trying their best to comfort her. Now knowing this, they would try their best to see from her perspective on things.
•After that they tried to include her more in their activities. They both understand she hasn't presented, but why not try and make her feel included? Moon started to show the things she liked to do as an omega. Like making nests and collecting things. Explaining some of her feelings as an omega. Reader of course hung on to every word she said. Robby tried to explain how his emotions and instincts worked. Telling her and even showing her some things alphas like him did, like extreme exercise and scenting. It wasn't long until they were actively courting the girl. Adding them into their own little pack. They didn't know what it would be like to be an alpha/omega couple with someone who hadn't presented but they still tried to make it work. It was a learning process for all of them. 
•One day they were at Moon’s house having a day in. Just talking and cuddling together in Moon's bed. Robby scented the girls as they lay together. Moon pressed up against Reader’s side as Robby held them both from the other side of Reader. It was sweet and soft. Then suddenly Reader needed to go to the bathroom. She got up and moved towards the bathroom and closed the door behind her. For a while Robby and Moon just sat there, waiting for her to come back. But after a while they started to get worried when she didn't come back. They both got up and walked to the bathroom door. Moon gave a small knock.
“Reader are you ok? you’ve been in there a while. We just wanted to check on you.”
A soft voice answered back.
”I uh, there are some things happening in here and it’s kinda embarrassing….”
Moon and Robby sheared a look for a second before a light went off In Moon’s head.
“Oh Honey did you get your period? I have pads under the sink or tampons-“
“That’s not it- it’s something else…”
“Can I come in? Robby can stay out here of course.”
The lock on the door flipped and the door cracked open, but that was enough for them to smell it. Moon slipped on before Robby could instinctively poke his head in.
•Moon knew what was happening the moment she stepped into the bathroom. The thick scent that covered the room had her head fuzzy. Just one look at the girl who was now panting while cupping her self on the toilet had her knowing what was going on. She was presenting, as a omega.
“Moon it hurts, and it….it won’t stop leaking down there. I’m so hot. Moon~” the soft girl whimpered, her thighs clenching. Moon softly smiled as she walked up to the girl. Eyes soft as she looked down at her.
“It’s ok honey, your presenting as a omega. Your going into your first heat.”
“It’s probably because you where around me and Robby so closely today. Robby was scenting us a lot. He might have triggered you into your first heat on accident.”
Reader whinned as Moon kissed her on her warm forehead.
“Do you want Robby and me to make you feel better? You don’t have to say yes if you're not ready. First heats are extremely rough though so I want to give you options.”
“I-I want to feel better…please Moon it hurts….”
•Moon helps her clean up the best she can and leads her out of the bathroom. Robby is clearly excited as he smells the newly presented omega. As soon as they are out of the bathroom he is sniffing her up. Taking on the new scent of his newest mate, it’s so sweet it makes his teeth hurt a little. He wants to fall into her scent and bathe in it forever. Moon guides her to the bed and lays her down, she’s basically limp as it is. All she can do is whimper and purr, asking for help.
“She’s gone into heat and she wants us to make her feel good.”
“Was it because I was scenting her to hard? Did I do this? I didn’t meant to…”
“Robby don’t do that, she was going to present at some point. This was probably the best time anyway because we are both here to take care of her~”
•Moon is quick to strip along with Robby. She makes a show out of stripping Reader of her clothes and tossing them on the floor. Reader is flustered as Moon starts to play with her naked body. Playing with tits, groping and squeezing them. She pinches her hard nipples and tugged at them. Her hands move to crease her soft belly, tracing her soft skin and rolls,grabbing her. Her fingers move to play in her wet puffy pussy lips. Her folds are drenched and slick spills all over, it ruins her thighs and ass. It’s warm and sticky as it flows from her hungry hole. Moon smiles and bits her lip as she plays with the girls engorged clit and then spreads her folds. Her finger tips slide into the twitching hole of her pussy.
•Reader squirms in pleasure as the other omega plays in her sopping channel. Her fingertips grazed over the spazzing walls of her cunt. Suddenly Reader jerks and squirts around the two small fingers that were buried inside her. It sprays and splatters over a standing Robby who just moans at the warm fluid. It coats his hard cock and already growing knot.
•Reader shivers in a cold sweat as Moon removes her fingers. She shoved them in her mouth and sucks on them. Moaning out in bliss because it’s a sweet but savory taste. It’s thick and warm and coats her tongue. She smiles at Robby who watches her lick and suckle at her fingers. He bends over the two girls and gives Moon a deep kiss. Tongues dance as they swap spit. Robby sucked up the new taste that is Reader’s slick on Moon's pretty tongue and lips. They pull away and moan out together, getting lust drunk on the omegas taste. A moment later he is bending down to kiss Reader as well. She squeals into the kiss as his cock rubs against her.
• They only part when it starts to become too much for the both of them. Moon reaches down and helps pull Reader apart, lifting her thick thighs and legs in the process. She kisses along the new omegas cheeks.
“Don't worry, Robby will go really slow and let you get comfortable. You're so wet that he can slide right in with no problem. Just relax and let him knot you.” She all but whispers to Reader who can only nod. Her eyes going up to look at Robby who is guiding his dick though her wet folds.
He slowly pushes in, tip popping through her tight ring of muscles. Her channel clenching around him as he pushes in. He holds onto her legs as he bottoms out, his knot popping in but quick to slide out with every new thrust.
•It only takes a few minutes of Robby fucking her brains out to get her screaming. Tears poured down her round cheeks, eyes threatening to cross. Her cunt is creamy and thick as it spills slick and her own cum. It coats everything near her, her mound, belly, thighs, and legs. It makes the sound of Robby’s hard thrusts even louder. Robby is gone as his mind is clouded by lust and her scent. He can't stop the way his hips grind against her or the way his balls wetly slap against her ass. The tip of his dick slams into her cervix but she barely feels it because she's so out of it. Her brain lust drunk by now. A few more thrusts and Robby’s knot finely swells enough and pops in, locking the two together. He growls above her and ruts into her. Knot swelled and his orgasm was moments away. Finally he unleashes rope after rope of cum into her, she finally goes lip as she has a boneless orgasm against him. Her walls clench and flutter as she cums around him.
Moon smiles as she watches them. Her eyes moved between the two and the girl's slowly bloated belly.