Well at least with Iroha (15) and Yachiyo (19) they are both teenagers and only a four year difference compared with Mami (15) and Nagisa (9?). Although given what magical girls do in the Madoka universe even that isn't that bad.
^ Grani's drive to protect Carol definitely makes that a stronger ship than Grani x Skadi imo. Pretty precious, those two.
I have neither Skadi nor Spectre but I am hella interested in their relationship, especially with all the high quality art around. I might go ahead and suggest them here.
@A-chan
There's actually a fanfic on AO3 called Virtual Union that has them do exactly that.
Well, not an official one, but there's a ceremony with friends, and a marriage ring, so that's gotta count, right?