"There is no normal, only average."

As for the biological part, it is my understanding that there are some evolutionary benefits to having a certain proportional of homosexuals in the population, although I don't know the details of why. But if this is so then homosexuality can hardly be called abnormal, it's simply natural selection "working as intended" to borrow Marvo's words. No, it's not evolutionary beneficial to the genes of the individual that happens to be homosexual, but it's not as if most people care about that.