Why Some People Are Homosexual?

There can be many reasons. They can simply be born being homosexual, mainly because of hormones, they can start liking people of the same sex because of traumas they had...

Some people think Homosexuality is a disease, or a mental illness. Not true. Imagine if people thought you were sick just because you were married to a lovely woman/man (opposite gender), this mainly happens because people were raised in highly religious environments (like a catholic family, that think that it is a sin), or simply because they are not used to homosexual (bisexual, pansexual...) relationships.

You cannot change the fact that you're attracted to the same sex, as you can't change if you're attracted to the opposite sex, or even both sexes, or sometimes not distinguishing both sexes at all(pansexuality).