So to start off with, I think most of the acting in this movie was excellent, and the cinematography was quite good. Also, the actor playing the nephew is really hot, so it was enjoyable whenever he was on screen.
The problem here was mostly the writing. It's overwrought, it's too on-the-nose, and it's just bad. I was expecting a sweet love story over time, and instead it's mostly a story about an elderly gay man's relationship with his sister, who embodies every stereotype of a homophobe. There's no nuance in any scene, and she doesn't go through any believable transformation. Scenes which should have been deeply emotional were made almost comical by their lack of subtlety.
Most problematic is that we never really see the main couple fall in love. We have a few scenes of them in their youth, spread out over years, and they're nice, but sparse and limited. The actors make you believe their feelings, but we don't get to see how they developed.
There are also numerous sound problems. Most glaring is the sound editing. In some jumps between shots in the same scene, the sound dramatically changes, as if there was nothing done to smooth the transition between a boom-mic and voice-over, but aside from that, the score is not good. Music sometimes drowns out the scene, and like the writing it tends to be overwrought.
This is a story that could have been really good if it had been handled with some subtlety, but the whole effort is too heavy-handed. As I've said, the acting is generally very good, and there are some genuinely moving moments, but overall it's not worth the time.
(Also, as at least one other reviewer has mentioned, the casting of the older actors isn't great. I don't really mind that too much, since finding someone to portray old Steve Salt without waiting for Steve Salt to get old would be hard, but the older actor looked nothing like him.)