This is a flawed but interesting and unusual movie, and I can understand why even the many positive reviews it gets have trouble describing it. Fighting that battle while trying to enjoy a movie must detract a lot from the enjoyment. People who say it's easy to forget that Francisco and Thomás are brothers in the latter half of the movie must be TRYING to forget it, because the movie never stops affirming the fact that that's what they are.
I don't feel compelled to try to twist it into something else that's more acceptable. I've never been at all attracted to my own brother, but two brothers' falling in love in a movie does not make me the least bit uncomfortable. I'm not advocating gay incest, but horror at the idea of sex between brothers – even in a movie, and even among gay men – mystifies me. That particular taboo makes no sense to me. It's not as if they would produce deformed offspring. I don't understand why mutually consenting sex between brothers near the same age is a big deal.