Tim, despite being a beta, may have inherited some alpha traits from Jack.
He's quite possessive and territorial with Bernard when he's about to go into heat; he wants him to wear his clothes, and he gives him lots of hickeys on his neck... Tim wants to get him a collar with the letter T to keep any alpha away from his omega.
Yes, Tim is just a beta; he doesn't have his own characteristic scent like alphas and omegas. But he's prepared to break the arm of any alpha who thinks he has the right to disrespect Bernard.
Continuing with the Omega!Bernard post about A/B/O Timbern:
Bernard disguised his scent using cheap cologne during his school years. Everyone assumed (even alphas and omegas) that he was faking his scent, but on the contrary, he was hiding it.
His parents didn't know Bernard was an omega; they only found out when they kicked him out of the house.
The Cult of Dionysus recruits through scent, as this makes them seem trustworthy to the omegas and alphas they seek to recruit, since a scent can't lie, right?
The cult assigns different "missions" to its omega members, one of which is to suppress their scent for extended periods, regardless of the consequences. This led Bernard to stipulate that he can only release his scent during his heat or when he bleeds due to the cult's "trials."
By suppressing his scent, Bernard's scent became so thick and intoxicating, almost like a drug that could affect even betas. That's why he became a candidate for sacrifice.
When Tim and Bernard start dating, his heat tries to regulate itself and sync up with Tim's rut, but Tim is a beta. His heat becomes irregular due to the abrupt change, since he was exposed to the alphas within the cult for so long.
Bernard went from having an scent of red fruits with hints of mint, to having a fermented aroma with black pepper.
Bernard tries to steal some of Tim's t-shirts and hoodies, almost stealing his entire wardrobe because his heat becomes intense and lasts for a couple of days (it was his first heat away from the cult).
Bernard still has Tim's bag of socks and Darla's hair ties.
Tim frequently checks the "Beta/Omega Couples" subreddit for advice.
The Drake family has had alphas (Jack was an alpha). The subgender isn't necessarily hereditary, but behavioral traits can be inherited. Tim can perfectly sense when an alpha shows interest in Bernard and tries to court him with his scent. He acts very territorial and jealous, like an alpha.
The first time Bernard invited him to his nest, Tim couldn't understand why he felt at home, since it was just piles of his and Bernard's clothes, and besides, he fell asleep and didn't patrol that night.
When Tim wanted to participate in Bernard's heat, Bernard warned him that they could spend it together during or after the third day, as the first few days were the most intense. Tim, confident in his physique, went on the first day... He returned to the Batcave after several days, dehydrated and sore, but quite happy.
Some extra facts about the Batfam:
Most of the Batfam are betas, except for Jason and Damian, who are alphas. Cass is also a beta, but because of her vibe, she's often mistaken for an alpha.
Tim doesn't ask Bruce and Dick for advice about their relationships with omegas, as he knows they didn't have good experiences and their advice might be biased.
Jason is the only one with a stable relationship with an omega, but even then, his relationship with Roy is atypical of an alpha/omega pairing. The only advice he gave Tim was not to bathe during his heat and to drink plenty of water.
Damian recognizes Bernard as Tim's omega, so in his pup mind, he's an important part of the pack. He also scares off alphas who try to approach Bernard when he's out with them.
Continuing with the idea of Omega!Bernard x Beta!Tim.
Tim is looking for exactly how he smelled in high school; although betas don't have their own scent, they can be associated with a scent. This can be done with the scent of the laundry detergent they use or if they use some kind of fragranced shampoo.
He wants to help Bernard get through his heat with less pain, and that's why he needs to find the scent Bernard associated him with in high school... But the bad experience within the cult made Bernard forget which smells he associated with his first pack bond.
Tim tries to remember the products he used in his teens and shows them to Bernard if they remind him of anything, but there are no positive results.
After Damian's soccer match, Bernard finds himself quite close to him. Before either of them can say anything, he starts rummaging through Damian's sports bag... And he finds a talcum powder from a brand that makes them scented, "This is what you smelled like in high school."
Tim feels stupid, of course Bernard will associate him with the smell of talcum powder because he used to steal his socks for his nest.
Throughout high school, Bernard claimed he would be an alpha, until the results came back and he was classified as an omega.
Male omegas are quite rare, so he does his best to keep his true gender hidden and pretends to be just a beta. He's careful enough to conceal his scent and excuse his absences from school by claiming he's "sick."
After doing some research on how to get through the heat without so much pain, according to experts (from Reddit), making a nest with clothes or objects from the pack and/or partner helps to confront and feel safer.
Bernard doesn't have a pack; everyone he knows (including his parents) are betas, so he can't ask them for something as embarrassing as an article of clothing. However, one day in the gym showers, he stares for a long time at Tim's socks inside his sneakers. According to the experts, shirts and hoodies are ideal, but stealing a t-shirt from Tim would be too obvious... but socks! Everyone loses their socks!
He steals Tim's socks and one of Darla's hair ties, and his heat passes without so much pain. So, when he feels his heat coming on, he steals a few pairs of socks and puts them in a cloth bag along with some hair ties to use as a sort of comforting pillow. And he returns the things to each of their lockers.
Unbeknownst to him, Bernard formed a pack bond with his friends by using their belongings for nesting, even though they were betas.
But Darla dies, and Tim disappears from his life.
Bernard becomes a packless omega with a broken bond... and that makes his scent of loneliness and helplessness so alluring and intoxicating when he's punished within the cult of "The Children of Dionysus." There's a morbid pleasure in hurting (until he bleeds) a broken omega trying to stay on his feet, making him a candidate for sacrifice. Bernard doesn't mind being a sacrifice as long as he can feel even a fragment of belonging to a pack.
...or so he thinks, until he runs into Tim again.
Robin saves him from the cult, and Tim asks him out on a date. Bernard can get his life back on track, study gastronomy, and have a romance with Tim.
Meanwhile, Tim can't find the hoodies and t-shirts he regularly wears, until he sees Bernard a few days later wearing one of those hoodies…
