Link and Mercury [Background]

I've got solid foundation for Jason and Adam. I want to work on connections to Charlotte and Harry too.

For Mercury, what does he want that his family can't or won't give him? I imagine there's a lot. Even if he's happy with his legacy, it's probably the same familiar stuff. It sounds like there's a repertoire of family speedster tricks. Can he learn new stuff on his own, if he tries? Does he want to? Would having a new sparring partner - or three - be helpful? Link and his robots can fight as a team or mix things up. Would the rest of the PCs want in on that kind of training?

Does Harry ever get tired of being recognized? Leo might be able to help with that too. New hangouts, new activities.

And of course, if he's happy as a crime fighter and dedicated to the cause, Link may remember useful things from his childhood: facts about Rossum, about other villains the Minion Maker sold product to, or "shop talk" he may have overheard that villains would only share among themselves.

If none of this sounds interesting, but you have some ideas, let me know!

That all sounds pretty good.  I think the one that connects with me the most is him being recognized.  All his life, Harry has been told he needs to uphold the speedster legacy.  Everything he has taught is so that he can do that.  He never really has gotten time to hang out and just develop himself on his own.  If it isn't school work, its speedster training.  That essential period of his life where he figured out who he was was taken away and he was told who he was.
And because he is the legacy to the speedster family, everyone knows him.  They know his parents and expect him to be like them.  He has always been Mercury, the superhero, before being Harry, the teenager.
I can definitely see Link and Harry going out for a night of new activities and stuff.  I guess that Link is used to going around unrecognized and he certainly has different hang out spots than Harry.
Is there anything Harry can do for Link just let me know.

Time to have some fun then! Sports shows, movies or concerts as a group, or taking a more active part like playing in sports (or forming a band!), street racing, or other cool stuff.

Harry can do a lot to help Leo out, but the first and best is just be his friend. He's strongest when he has friends and something to fight for.

Aside from that, Leo's got a plan. He's going to try and rehabilitate the supervillains we encounter, if or when that seems possible. Harry could be amazingly useful in that plan. How? His parents, and their superhero connections, might know something vital about them. Civilian family members, the truth of their villain origin, friends, rivals, whatever. Anything that'll help Leo reach these people who could be helped.