Ages are kind of difficult to say - Kota is a young adult, I think 21 or something? The only ages given on the official site are for the four main Riders and Mai. They're just kind of collectively called "the youth" so I figure a fair age range to guess is... post-high school, pre-collage? That'd mean they're not in school which would make a lot of sense.
As for parents, I can definitely see that being a flaw. Kota's got an excuse at least in that his parents died.
I think the forbidden fruit was already given to Kouta, since the Kiwami Arms embodies all the power of the lock seeds. I don't think the other riders has realised yet that he has gained the fruit,
When we got episode summary scans about the episode the Kiwami Lockseed appears in... the wording was weird, sort of vague if I remember, but it seemed to imply the forbidden fruit was used to create the Kiwami Lockseed, rather than being the actual fruit itself. So if that's the case, no one has it yet.
A second opinion would be nice now that we have summaries on TV-Asahi's site.