Not every headcanon concerns major ongoing plot or character twists. Some would probably never show up in the pages of Sentinel Comics. But all headcanons are good, and sharing is caring, so let's share ours!
Expatriette is vaguely non-monogamous. She's fine with just Pete, but she needs a lot of alone time, and she kind of wishes he had someone to do more traditional boyfriend/girlfriend stuff with. Pete would be fine with just her, but occasionally gets pestered into going on awkward dates with other women while Amanda sits at home, drinking beer and target shooting.
Nightmist and Harpy's costumes are based on outfits they chose for each other to go clubbing in. The pair of them have occasionally taken advantage of their increasingly rare downtime to check out any decent goth clubs they can find. Absolutely nothing should be read into each of them independently dressing the other in the shortest skirts they could find. They're not a couple. They tell us so constantly. Often without being asked.
Legacy speaks excellent Spanish, and is trying to learn as many Native American languages as he can. He's rarely got the time to focus on lessons for long, but he's doing his best.
Parse isn't really interested in romantic relationships, but she does have an aesthetic preference: beautiful dumb men. Particularly beautiful dumb men who get adorably flustered when they don't know things. Needless to say, she finds Setback almost unbearably cute.
Since Ermine first realised that he could do it, she's basically insisted that Fright Train carry her everywhere. Cassandra Lilya constantly bombards her parents with pictures of her and Steven Graves doing romantic date things, because she knows they hate it.