By "pro-homosexual evidence", do you mean data that suggests that homosexuality is not an acquired trait but rather a congenital one/one that isn't acquired?
As others have already pointed out in this thread, there are some animals which have been claimed to exhibit homosexual as well as bisexual behavior; however, what I'm going to talk about here is different in that it presumably comes from Muslims who are homosexual themselves. They sent questions to Islamic websites asking for help because they had to curb their sexual desires, and some of them even told of how they cut off ties with their friends to avoid arousing their sexual desires.
The aforementioned questions and their answers are in Arabic, so I'd have to translate them for others to see, but I'm not sure if most people would like to read those; I know I didn't feel good at all while reading them.
Also, if we assume that some of the people who sent those questions were non-Muslims pretending to be struggling homosexual Muslims just to make Islam look bad and/or cruel, that will still not explain the number of people who posted about their ordeals there: there were at least 50 posts in the comments section of one of said questions, and a lot of them mentioned similar problems with their sexual desires. I strongly doubt that they all lied, especially considering that a lot of the posters seemed sincerely struggling from their tones.
At least two questioners also mentioned that they were never subjected to any kind of sexual abuse... that they were raised in a "completely normal" environment and in very healthy households -- and at least one other questioner said that he had seen more than one psychiatrist to help him, but all of the psychiatrists he had seen told him that "we have no cure for this disease as this is the nature of a homosexual person", i.e. it is not an acquired trait that can be changed or "cured" in some way.
Once again I iterate that I didn't translate any of said questions or answers then posted them here because I felt deeply disturbed while reading them, and I strongly suspect that this would be the case with most people here, which is why I went with reported speech instead.