The Guy in the Window — Cara Dee

Everett is in the middle of a nasty divorce when the adopted son of his estranged brother messages him on Facebook. He's kind of a dick at first but Adam shortly becomes "sort of" his nephew, then the guy who helps him find an apartment in the building next to his, then the guy who helps Everett patch up his relationship with his daughter.

Then they fall in love, natch. It's a sweet, sexy story with a bit of pseudo-incest thrill and an age gap.