Queer is sometimes used to describe a fluid gender identity. Transgender : A person whose gender identity differs from the sex they were assigned at birth. Some parents are open and accepting. Girls who have sex with girls can get STIs. Many adults and teens have never had sex with a person of the same sex but still identify as gay. Puberty : The stage of life when the reproductive organs start to function and other sex features develop. Some teens may question their gender identity for the first time during puberty.