Someone can't be ''gay bisexual'' as homosexual [gay] means being attracted to only the same-sex, whereas bisexual means being attracted to both sexes/all genders. Somebody can be bisexual same-sex leaning (or opposite-sex leaning), however. ''Gay biromantic'' refers to someone who is sexually attracted to the same sex, and has feelings for the opposite sex but doesn't register this as sexual attraction.
Hm... I'm guessing you mean like homoromantic bisexual. That would be if you're sexually attracted to two genders, but romantically attracted only to the same gender.
