It isn't a specific sex act that determines if you're gay, nor interest in a particular body part. It's the gender of the persons to whom you're attracted, and of the persons to whom you are not attracted. To be gay, this means being sexually attracted to males, and not to females. Bisexual is when you're attracted to both.
But an essential part of male sexuality is his equipment, and I really haven't known any gay guys who had no interest in it at all. Or even puke at it? Do these 2 friends have any involvement or interest regarding women?
But some straight guys like BJs enough that the gender of the mouth giving one doesn't matter to them. And likewise, they can fuck any hole of opportunity.
So what makes you think your friends are gay? What gay behavior do they demonstrate, other than getting blown by gays and being tops? Do they like to ogle guys, and like any other male body parts besides dicks? Have they any straight sexual behavior & traits? Such as being interested in women, having straight men's adult reading material, and wanting to puke at the thought of touching another man's penis?