I've always wondered that, too. I feel like things were intentionally vague for a lot of things, because the amount of time that had passed was intentionally vague. But then it just gets confusing with sibling ages. o.o Like, I always wondered how old Tom was. He's in high school when the series starts. Is he still in high school in the final arc? If he'd just started high school in #1, then he'd probably be in his last year. Which... would make sense except Jake says Tom joined the high school basketball team, and had also been weirdly distant for a year. Unless Temrash was like "yeah, can still do this b-ball thing for awhile" and then quit, Tom's been off the team for a year. Which means he has to be at least a sophomore in #1.
So... did he graduate? Was he taking college classes? Was he taking a gap year? IT DOESN'T SAY.