A heterosexual who is in a relationship with someone of the opposite-gender is a heterosexual
A heterosexual who is in a relationship with someone of the same-gender is a heterosexual who is acting against his/her orientation (nature?), but is still a heterosexual
A heterosexual who is celibate is one who is celibate, but still a heterosexual
A homosexual who is in a relationship with someone of the same-gender is a homosexual
A homosexual who is in a relationship with someone of the opposite-gender is a homosexual acting against his/her orientation (nature?), but is still a homosexual
A homosexual who is celibate is one who is celibate, but still a homosexual