These are gonna be a mix of headcanons from when he was a kid up to his epilogue age
He was a DC and Marvel fan since he was a kid, and discovered comics after his dad gave him one one day after he came back from work and gave it to him, ever since, bill was hooked
Was the kid that was obsessed with Spiderman and batman and would beg to have everything themed as them, from his room, his clothes, pajamas, shoes, etc
Definetly tried to get bitten at some point by a spider, hoping he'd get powers
Even though he loved DC and Marvel, instead of wanting to talk about it with others, he was definitely the type to try and gatekeep everything, as he wanted to feel cool and special that only he knew about it, especially after he got into comics and wanted to feel like he was mature for reading them
His dad had a liking for comics too, and his mom wasn't into it, but bill still talked about it to her while was cooking or doing chores. He had a good combo for parents (at least in his eyes), as he went to dad for comics and his interests, and mom for love and comfort. This is why the divorce seemed sudden to him, since he always thought his family had a good dynamic (or could've also been plain child innocence, as he was too focused on his own thing, and cause his parents kept the fights private)
when the divorce finally happened, it was a total shocker to him. it happened around when he was 8. he was little and honestly shocked at just the idea that he was watching his dad walk out that door with suitcase in hand, and with the idea that he was never returning
he was quiet for a few days, just processing what happened and trying to understand why it happened, what went wrong, and what HE did wrong.
he had a pretty good relationship with his dad, so he wondered if maybe jane or his brother did something, or maybe even his mom
him and his mom were close, he had always been a bit of a mama's boy after all, but at the the same time, he couldn't see why his perfect mom could possibly drive away his dad
that was until his mom didn't have time for him. in his eyes, she never paid any attention to him anymore. She was always busy or too tired, and it just made him start to believe, "Is this why dad left? did mom treat him like this, too?"
of course, he didn't know that his mom was just doing her best to pay the bills and to give her 3 kids a comfortable life. in his eyes, she was absent because, in a way, she was, even if not by bad intention
this led to him becoming more bitter and blaming her for his dad's absence, and he just became more and more resentful as he grew up. he focused on his collections and his comics, the only thing he had control over, and the only thing he had left to remember the good times with his dad and his mom before everything was ruined
when he had his group of friends with pete, jerry, and josh, he immediately made himself leader, both to have that sense of control, and that sense of "i CHOOSE when i want to leave" feeling. he could choose when he had enough, he could choose to stay or not; he preffered to be the one to leave and kick others out of the club when HE deemed it necessary, instead of being left to the side (again)
he slowly became rude and egotistical as he grew up, getting that sense of superiority the more control he gave himself, from his comics, his collections, his friends, his club, and slowly, his "career" as well as he got older
he slowly became spoiled as well, as his mom would try to compensate with material things to try and fill in her shortcomings. it didn't fill that void that Bill already had, but at least he got something, and slowly got the idea that others had to compensate him as well for their shortcomings
he was rude, egotestical, and sometimes even just plain cruel.
he also started to become the type of person where he couldn't see other happy because he became jealous, believing HE deserved it more, not them. so much to the point he would do ANYTHING to get it. which is what led to wanting the same "power" as joe had; of running his own comic book store, to be the "king" of the very thing he loved
when it came to dating as he was older, it never led to anything due to how egotistical he was, as he always had such high expectations, yet he didn't even meet the bare minimum for anyone
he was the type of guy to expect his partner to cook for him, do his chores, make the money, take care of him, and fulfill every whim and desire he had in bed. he is basically like a mom with benefits, yet he denies that that's what he wants and tries to give it a more appealing and "masculine" label that makes him look good.
he basically sees himself as the trophy husband because ANYONE should feel lucky and even honored to be his (according to him)
he is also absolutely a big cry baby. not in front of others (unless you break him enough), but he breaks down a lot at home. when he cries, it ain't pretty either. if he's doing it out of anger or frustration, he would throw a full-on fit, like throwing stuff, yelling, screaming, and maybe binge drinking until he passed out
if he cried out of actual sadness or heartbreak, it's more of a whailing and sobbing type of breaking down, like snot and tears down his face while he's on his knees