My cousin is gay

My cousin is gay, I first discovered he was gay when I was like 11 yrs old and me and him had very different tastes in porn. He liked gay porn, I liked straight porn.His sister (also my cousin) confided into me that she too knew he was gay.That was 15 years agoSince then everyone has accepted that my cousin is gay. His mom knows, his aunts and uncles know, his grandparents know, his nephews know, I know, everyone knows!About 10 yrs ago he met a really cool older guy who really set my cousin straight. Ever since then my cousin has been doing really well...this guy is cool and has been able to clam my cousin down (my cousin was a trouble maker growing up)Well this man did him right and my cousin is better of because of it.So...here what I don't getMy cousin has never said he's gay, hes not bi (no one has ever seen him with a woman, romantically) and he's been living/dating this same guy for like 10 years now. Everyone is accepting of it...know what my grandpa said on his death bed 3 years ago to my cousin boyfriend?"I'm glad (my cousin) found someone that he spend the rest of his life with" my cousin was there, his boyfriend was there. Actually my cousin boyfriend played A MAJOR ROLL in assisting our family with the death of my grandpa. And even before then we had treated my cousin boyfriend like family.That came from my homophobic, racist grandpa (he was in his 80s, he grew up in a different time)But what gets me is I just got off the phone with my cousin and I straight up asked him "Why haven't you admitted your gay?"To me is strange, everyone is accepting and understanding. No one is hating on my cousin.In fact myself and others have often said "The last person to understand that (my cousin) is gay is going be (my cousin)"I don't get it, also he's never come out to his sister, mother, or anyone in our family. He even insists that he's straight.I'm sorry but straight men don't have a romantic relationship with other guy for 10+ years.So any insight? It seems odd to me.If you guys are wondering why this is important to me is because my cousin has issues, and I think one of those issues is that he thinks he should be straight (but he isn't) yet everyone in our family is accepting of his sexuality.