Back on it with my headcanons once again, this time with all the kiddos. (and no, you didn't see that post that I surreptitiously deleted I've no idea what you're talking about)
Spider and Neteyam are both opposites. Spider is the reckless, adventure seeking older brother, whilst Neteyam is the responsible thinks before he acts older brother. So if they're spending the day together in the forest, Spider is likely to go climbing up a tree, whilst Neteyam calls up to him from its roots to be careful.
It's the same when you add in the younger siblings. Spider feeds on their chaotic energy, usually playing games of chase, or hide and seek when they're meant to be getting ready for bed. Whilst Neteyam sits quietly, either with Lo'ak or Tuk in his lap.
When Lo'ak was born, it took a while for Spider to grow used to him, and even longer for Lo'ak to like Spider. It was often Neteyam who would hold the baby, and Spider would mind Kiri because they bonded quickly. But then, at the age of 4 Lo'ak (stupidly) gets lost in the forest, and Spider is the first to find him - mostly because he thought to look in the roots of the great trees rather than under bushes.
Kiri and Spider have a special relationship, in the sense that when you get them together in one room, the energy levels will climb exponentially until their smiles are so wide their cheeks hurt, and their laughter so loud it can be heard at the bottom of Hometree. They can have their quiet moments too; when they're tired, they can often be found sat together braiding each others hair, or napping with Spider wrapped around Kiri's spread eagled form.
Tuk, when she's old enough, refuses to be treated as a baby. Even though she's the youngest. She talks back to Neteyam when he suggests something, teases Spider as much as he does her, even treats Lo'ak as her personal pillow. But, she still loves her older siblings; she will happily sit quietly with Kiri in the company of the forest, joins Neteyam on his ikran for a short flight, goes with Spider to see [spoilers], and badgers Lo'ak to play with her daily.
When their parents are out on date night, it is usually Spider and Neteyam who mind the younger ones. Although, again, that turns into chaos. Mealtime becomes a mess, because neither boy knows how to heat the food their mum left behind so they end up going to Mo'at. Washing up takes an age, because Spider finds it great fun to splash his siblings and start a water fight. And bedtime almost takes an hour. However, by the time Jake and Neytiri return home, it's to the adorable sight of the kids tangled together in a cuddle pile like nantang pups, their arms and legs tangled and Neteyam stuck at the bottom.
Tags (let me know if I am bothering people with these please): @be-the-glenn-to-my-maggie @spicymiilk @tuberculosis-chic @lloyd-007 @fluffygreenkoala