Peter Parker/Spider-Man and Mary Jane Watson originally got married back in 1987 and remained (mostly) happily as such until 2007. That year had the infamous, "One More Day," event where Mephisto/the Devil, basically, undid their marriage retroactively in exchange for saving the life of Aunt May--she'd gotten shot when someone was trying to kill Spidey. The whole thing also undid Spider-Man revealing his identity to the World as a bit of a soft reboot. Many fans hated it and demanded since it occurred that Marvel undo this change. A lot has changed since 2007, and Peter and MJ were a couple at points, but no wedded bliss occurred. Until now. Kind of.
The Ultimate Universe has returned in a tweaked form. The Reed Richards from that dimension was one of the few survivors of the realm (along with Miles Morales) and they came to the mainstream 616 Marvel Universe. He escaped to a new place and made some tweaks, however. A part of those tweaks seems to be that Peter Parker won't be Spider-Man until he's already older...and has a wife and kids. That's right, the marriage is back!
This is a big deal for those who grew up with Spider-Man married and even though the Universe and origins have been tweaked, that fact we've got a grown-up Spidey with MJ and kiddos is pretty cool. Plus, Jonathan Hickman is writing this and he's a stellar storyteller so that's awesome. Marco Checcheto is doing the art and I'm a fan of them as well, so this is shaping up to be another interesting piece of the newest iteration of the Ultimate Universe!