@Sqad / Tony
Homosexual behaviour has been observed in countless species - well documented examples. So whatever your personal opinion about such behaviour, it is not unnatural.
And regarding the evolutionary advantage - you are thinking far too literally, Sqad. Several theories explain the genetics of homosexuality, and can be linked to an evolutionary advantage. And try to remember that evolution is blind, and its effects need to measured across a species, rather than an individual of that species.
Among the more common hypotheses - one that posits homosexuality as a kind of unintended consequence of an X-linked allele that codes for female fecundity.
Another hypothesis, based upon the observation that there is a higher level of homosexuality in families with a large numbers of male children, particularly the youngest, have suggested that this can be linked to maternal anti-male antibodies which prevent the full masculinisation of the foetal brain (fraternal birth order defect).
Human sexuality is complex, with the fundamental orientation established by genetics largely at foetal stage; There is a degree of plasticity which can allow for a range of sexual behaviours to imprint upon that basic orientation.