When Thor was living as the lame human doctor Don Blake, Jane Foster became his nurse. She loved him and he loved her, but she couldn't admit her feelings because it was the '60s and ladies didn't do that, and he couldn't admit his feelings because he found it inconceivable that a woman like Jane would ever love a cripple. Then Don went to Norway and found the cane that would turn him back into Thor, learned of his true life as the god of thunder, and was still in love with Jane, who was more than willing to return Thor's affections. But Odin didn't like the idea of Thor being in love with a mortal, so he first reintroduced Thor to Sif, a fellow warrior and an old flame who had waited for him during his exile on Earth. Thor remembered her but was still in love with Jane. So Odin granted Jane godhood because he knew it would overwhelm her mortal senses, which it did. She was suitably scared away and she and Thor basically broke up.
Thor and Sif didn't get back together right away, though. Thor still pined for Jane a bit, so she was cool and let him deal with his stuff. Then Jane wound up on the verge of death and Sif, realizing that Thor still loved her, merged her soul with Jane's, effectively sacrificing herself so Jane could live. Jane recovered and eventually started displaying more badass tendencies due to Sif's soul. Then, for no apparent reason, Sif and Jane swapped places. They investigated and found that some evil wizard or something was messing with their connection, so the connection was broken and Jane and Sif were fine, but Jane lost her memory of Thor, Blake, and everything. She disappears for a while. Thor and Sif kind of flirt with a romance but never really appear to be a steady couple.
Jane reappears years later as the wife of Keith Kincaid, another handsome blonde doctor who bears an uncanny resemblance to Blake. Jane's memory is still dodgy, but Thor realizes she and Kincaid are in love and leaves them be. This is like the late '70s. Thor and Sif get back together then split up because Thor hits her while under a spell. Jane and Kincaid have a baby. Sif decides to date Beta Ray Bill. Thor bounces from lady to lady without any real commitment. Sif and Bill split up. Sif and Thor flirt with romance again.
Thor gets banished to some nether-realm for killing Loki and his then-human-host Eric Masterson takes his place as the new god of thunder. Eric, a divorced dad with part-time custody of his son Kevin, grows closer to Sif. Eric learns that Thor is not truly dead and decides to bring him back. When he does, Thor and Sif jump wholeheartedly into a relationship. Eric gets put under a spell that makes him want Sif and he and Thor fight over her. Thor soundly kicks his ass and retakes his hammer while Eric, free of the spell, is given the mace Thunderstrike. Eric dies after a short career as a superhero.
Thor goes through a whole bunch of stuff and he and Sif break up again (not sure why this time because this is an area of Thor's series I haven't actually read yet). The gods are stripped of their powers and Thor finds that the Enchantress can magically restore his powers. He and the Enchantress start shacking up shortly after this. Onslaught happens and Thor is one of the heroes who seemingly dies.
Heroes Reborn happens and then Thor and the other heroes return to the mainstream Marvel Earth, but Thor, due to a fight with Dr. Doom, is waylaid and winds up on some alien planet with a woman he comes to love. She dies (don't remember the specifics too well). Thor returns to Earth and promptly gets killed by the Destroyer. He must be bound to Jake Olson, an EMT who died in the crossfire of the fight, as penance for his carelessness in order to come back. Jake was engaged to a single mom, which creates a ton of problems for Thor. Jake's boss at the ER turns out to be nurse-turned-doctor Jane Foster, which creates more problems.
Thor's father Odin dies, leaving Thor to take up the crown. He and Jake Olson are split into separate entities, except the real Jake Olson's soul had already gone to Heaven, so the "Jake Olson" that appeared was actually Thor's humanity given form--leaving, for those keeping track, Thor
without his humanity. The humanity-less Thor takes the Enchantress as his queen, ultimately kills "Olson" for opposing him, and proceeds to meddle far too much in human affairs over the next few hundred years, culminating in a big cosmic do-over that requires him to rejoin himself with "Olson" and undo his previous actions. Before he goes back in time to do this, he stops before a frozen-in-time Sif and tells her, "It should have been you. Had I been whole, it would have been." (He also says goodbye to Magni, his son with the Enchantress, who will now never be born.)
Then Thor returns to the present and Ragnarok happens, ultimately destroying Asgard for what seems like the final time.
But then Don Blake pops back into existence and, realizing what's happened, reclaims Mjolnir and convinces Thor to return to the land of the living. (Blake and Thor are more separate entities with their own thoughts and opinions now than they were before.) He does so and eventually brings Asgard with him--except Sif, whose body Loki has hijacked. Her spirit is left in the body of a dying old woman under the care of--surprise, surprise--Jane Foster! Turns out Jane has divorced Keith and left custody of their kid to him. She sees Blake again and admits her feelings for him (note: him, not Thor) and Blake reciprocates. Thor continues searching for Sif before ultimately finding her when Loki reveals he's in her body (spinning things so that it seems like it was all an accident, of course). Reunited, Thor and Sif get back together. She sees Beta Ray Bill with his new girlfriend (long story) and resents him a bit, but then she goes back to doin' it with Thor and seems all right. So now Thor and Sif are together (or were, until Thor died again at the end of
Fear Itself) and the Jane/Blake thing has basically been dropped because, it seems, no one other than JMS was interested in writing about Don Blake again. Although, Jane did move to Oklahoma to open a clinic in the town Blake lived in and Thor put Asgard to float near.
That's probably way more than you wanted, but I can't stop once I get going.
