Have an aunt who has only ever lived with women. I was always told it was her roommate. Everyone refers to her as a roommate. They BOUGHT THE HOUSE TOGETHER. Have dogs together. Raise the other ones kids together.
When I was like 17, and openly gay, I straight up asked my grandmother if her sister was a lesbian. She said no they're just roommates and got super specific about it. I asked my aunt a couple weeks later when I saw her and she went "Well, yeah. Do I not wear enough flannel?"
Aint no way they dont know. They just lie to themselves and others because they think that being gay is something to be ashamed of. There is no way people are this oblivious for decades.
I've been impressively oblivious to things for quite long periods of time, so I wouldn't put it past people.