all of this sounds awesome to me and i'm so into it. rees is pretty soft-spoken so in the beginning he probably just went along with her being more structured but being a *~*sensitive artist*~* and pretty adept at listening, he'd have been able to see the more easy-going parts of her from early on. and rees would have been all omg babies about the twins, with all of his brothers and sisters he tends to relate to kids with less awkwardness than adults, but by that point billie had probably already seen him at his least awkward and most relaxed anyway. he's also the type that if he got a text that said 'i need something' he'd reply 'leaving now'. idk if it'd be something you'd be down with, but if you wanted to we could say they tried their hand at dating in the very beginning to get them actually spending "not mutual friend group" time together and then deciding pretty quick that they were much better as friends?