I think it would be hilarious if when Ed and Al joined team Mustang they just assumed Roy and Riza were married and like one day much to their confusion and sadness they find out they're not and the rest of Team Mustang has to be like we don't really get it either
Alphonse: Hey, what's Leiutenant Hawkeye's last name
Falman: What do you mean? It's Hawkeye. Riza Hawkeye.
Falman: H-A-W-K-E-Y-E, R-I-Z-A
Edward: Wait, I thought that was her nickname since she's the top sniper, "The Hawk's eye"
Fuery: Yeah, but her last name is also coincidently "Hawkeye."
Havoc: Honestly, that's probably where the name came from. The officials at the military academy aren't that creative.
Rebecca, with dramatic flare: Or maybe it was her destiny
Alphonse: So, is that why she kept her last name?
Edward: Why she didn't take the colonel bastard's last name?
Alphonse: Yeah, it could be confusing to have a Lieutenant Mustang and Colonel Mustang
Edward: Why do you think I call him Colonel Bastard, it's not just accurate but strategic
Rebecca: Oh . . . honey . . no
Edward: Why does everyone look sad all of a sudden?
Havoc: *puts a comforting hand on Rebecca's shoulder*
Fuery: The Lieutenant and the colonel . . . well . . . They aren't actually married
Rebecca: *starts crying on Havoc's shoulder*
Alphonse: B-but they're together, aren't they?
Rebecca: *cries even louder*
Havoc: *rubs her back comfortingly*
Breda: No, they're not - I mean, well
Alphonse: Why aren't they together?!
Rebecca, sobbing: WWWWHHHYYYY?!
Hakuro: What the hell is going on in here?!
Rebecca: *furiously screams something inaudible at Hakuro*
Later in Resembool they break the sad and shocking news to Winry who actually takes it a lot harder than they do because she ships them soooooo much