I'm going to be ~controversial~ here and say yes.
Shamelessly copy-pasted off Wikipedia:
Other studies mentioned on the same page suggest concordancy of around 30-50%, but even if that's true, that still implies homosexuality is not entirely genetic, otherwise it would be close to 100%. And of course, if sexuality is determined by social factors, then a person could indeed change.Among [identical] twins, 6.7% are concordant [that is, both express same-sex romantic attraction]. [Fraternal] twin pairs are 7.2% concordant. Full-siblings are 5.5% concordant. Clearly, the observed concordance rates do not correspond to degrees of genetic similarity. None of the comparisons between [identical] twins and others ... are even remotely significant. If same-sex romantic attraction has a genetic component, it is massively overwhelmed by other factors.
Don't think for one second that I support any efforts to pressure people to change though. A person's sexuality is a matter for them alone and they should not feel pressured or discriminated against.