When Tony is lying in that bunker in Siberia in his disabled suit, unable to move, HYDRA shows up. They had the place under surveillance and the chance of getting their hands on Tony Stark pretty much makes up for the loss of six Winter Soldiers. Tony is desperately trying to move, trying to figure out a way to get away, when suddenly whatever metal there is in the bunker starts attacking the HYDRA goons and then some of the X-Men (Peter, Alex, Kurt, …) show up and take them out. And Tony suddenly finds Erik Lehnsherr beside him, carefully peeling his armour away – apart from the chest piece because at this point the armour and Magneto using his power on Tony’s artificial sternum are all that’s holding Tony’s rips in place. After dealing with HYDRA, they bring Tony on the jet to bring him home.
At some point Tony loses consciousness because when he comes to he’s in a bed in a manor. Alex and Peter show up to reassure him that Erik and Charles are handling everything. And by the way, welcome to the family because he’s been adopted. Tony’s just staring at them. Peter takes it that he’s surprised by his similarity with Pietro, so he explains that HYDRA somehow got their hands on his and Wendy’s DNA, which they used to give Wanda and Pietro their powers. Tony however is still stuck on the part where he’s been adopted by Professor X and Magneto. Alex tells him that it’s not the first time one or both of them have pretty much adopted someone – after all it’s how he and his (biological) brother both joined up. Granted, it has been a while since Charles and Erik were the ones to quasi-adopt someone instead of some of the younger X-Men but hey, they get a new little brother out of it, so they certainly don’t mind. But Tony doesn’t understand why anyone would choose to adopt him. Peter and Alex point out that he’s so much like the both of them that he might as well be their love child (the way he, like Charles, believed in cooperation, in compromise; the way he, like Erik, was traumatized by the murder of his mother, …).
Erik and Charles suggest that he stays a while, so that he is protected from Ross while he heals. He agrees when they promise to have Rhodey and Vision brought to the Institute and offer to take a look at Rhodey’s injuries. (It’s not by chance that the X-Men he spends most of his first few days at the Institute with are Alex and Kurt and others who’ve also had a hard time believing that they might have found a place where they are accepted, that they have a family now)
After Tony’s recovered somewhat and can stay awake for longer than a couple of hours at a time, they ask him what happened. Tony tells them everything, including what he saw on the other side of the worm hole. And the X-Men not only believe him, they sit down with him and start planning, start calling on all their contacts to start preparing, start training.
Meanwhile on Asgard, Loki’s started to prepare for the coming war and is trying to figure out how to prepare the other realms as well without showing that he has information Odin does not have. One day after court General Tyr stays behind and calls him out – saying that he’s acting too reasonable and considering the good of other realms too much to be Odin. Loki is understandably defensive at first, demanding to know what he’s going to do with the knowledge that a Jotun monster is sitting on the throne. Tyr just calmly tells him not to talk about his mother that way, then explains that he, like many Aesir, like Odin himself, is part Jotun. Loki, still hesitant to believe him, asks if that’s why Odin adopted him. Tyr replies that he thought that, like with Thor, Odin had brought the result of one of his affairs home since Frigga can’t/won’t give him children. Loki even more confused now. He thought he was Laufey’s son. Tyr just shrugs. Well, yes, but some Jotun can both sire and birth children, so he, like many others, figured that Odin had had an affair with Laufey. Also, whether Loki is part or fully Jotun, someone really needs to explain Jotun biology to him before he gets into trouble. So that’s how Loki finds himself getting The Talk from Eir while Tyr calls the War Council so “Odin” can tell them about Thanos and they can start the necessary preparations.
Part of the preparation is contacting Jotunheim and getting ready to work with them, which is how Loki meets his brothers and Laufey’s spouse. Turns out that they don’t blame him for killing Laufey because the events of the war with Asgard (especially the loss of the Casket and of Loki) drove Laufey mad and he has not been acting in the best interest of Jotunheim for some time now. Also, for some reason, Jotuns not only don’t mind that he’s smaller and has magic and find it actually attractive and are trying to court him???
When Thor comes back to Earth with the Guardians and Bruce to warn them about Thanos and Team Cap are consequently allowed back, they are all surprised to find that Tony has the preparation on Earth well in hand (and is always surrounded by slightly overprotective siblings and fathers) while an alliance of the other realms (including Jotunheim and Loki, much to Thor’s surprise) are ready to help.
And somehow Thanos is beaten and Tony’s suitor (Strange? T’Challa? Peter Quill?) is left having to prove himself to his new fathers and siblings (including Rhodey) who are damn protective of the “baby” of the family. Tony pretends to be annoyed but secretly loves it. The public is not all that willing to accept Team Cap back, especially since they weren’t really needed in the fight against Thanos. Loki and his Jotun fiancé decide to travel the Nine Realms, now Thanos is beaten and Loki, as only third son of Laufey, is free to do what he wishes. Thor can deal with Odin (who’s just the slightest bit put out by what happened while he was asleep).