I don’t know the specifics, but I do know that even the youth vote is not “Safe D” in all locations; in fact, how parents vote may have an effect on youth political preferences in many cases. For example, some states conduct mock elections involving school-aged children, and these results have often mirrored actual election results - in 2020, mock elections among school-aged children in Iowa and Montana nailed the actual winners of the statewide contests in those two states that year.
If anything, it's become steadily less age-based over the past 5-10 years. Biden rebounded with the elderly and while Dems still win the youth vote, it's way off from Obama's 2008 margin.