Jorah Mormont continues to follow Daenerys Targaryen across Essos like a lovesick school boy despite the fact that he's, like, forty years old. Now by our standards that would make him a bit of a creeper, but by Westeros standards, he's being a total gentleman about it. Different worlds, folks, different worlds. In fact, Jorah's love for Dany looks to exist somewhere between desiring lover to doting father figure. Which yeah, in our world isn't any less creepy. But we digress.
For most of the novel, Jorah serves as Dany's advisor and bodyguard. He's older, wiser, and has seen a lot of the world during his days as a sellsword. He discovers that Xaro only wants to marry Dany to snag one of her dragons and counsels her to leave Qarth as soon as possible for the east (41.Daenerys.90). He also reminds her of the hard truths in life, like the fact that the people of the Seven Kingdoms will see her as an invader despite her rightful claim to the throne (41.Daenerys.106). He also protects her physically, rushing in to save her from Whitebeard and Strong Belwas before realizing they are allies.
Dany picks up on this fatherly persona, too. She thinks of Jorah as her "great bear" (28.Daenerys.21) and knows he will always think of her as his cub and guard her even if she is technically his queen.
After Dany and her people find Vaes Tolorro in the Red Waste, Jorah finally tells her why he beat feet from the Seven Kingdoms.
Jorah won the favor of his second wife, Lynesse Hightower, during a tournament he won. He brought his wife to Bear Island, and she quickly became miserable as the island lacks the class and style of city life. Desperate to make her happy, Jorah bought her jewelry, hired a top chef, and built her a ship for vacations abroad (13.Daenerys.75). Ooh la la.
When he bought his way into the poor house, though, Jorah sold slaves to help support his wife's habits, which is a huge no-go in the Seven Kingdoms. When Ned Stark came to have him answer for his crimes, Jorah and Lynesse fled to Lys, where Lynesse eventually shacked up with a merchant prince, dumping Jorah flat.
When Dany asks Jorah what she looked like, Jorah confesses, "Why, she looked a bit like you, Daenerys" (13.Daenerys.82). This quote helps explain the attraction Jorah feels for Dany as his affections for his wife never truly withered. He's a lifelong puppy it seems.