Umm...quite honestly H's parents know that something is going on..by definition they'd have to but they've never really made much of a big deal of it. To be honest, H's mother feels that I'm a nicer person now and has told me she is happier now that we (as in me, H & T) all seem to be getting on. She has hinted that she knows the precise dynamics of my situation but I think accepts it as she very much approves of T.
I think she, H's mother, views T's relationship with H was a reward for H & T dealing with my stupidity and pain and stuff like that and the effort they had to put it. H's father is quite quiet anyway and doesn't seem to express many views about anything.
Again, T's parents are pretty much in the same boat by all standards. They are not stupid by any means and I think they're happy to see T happy and settled and in a stable and loving relationship with H. To be honest though, T's mother is a very bright woman and very perceptive. I suspect she is aware of far more of the dynamics of my, H & T's relationship. I base this idea on the way she treats me in comparison to both H & T.
She does view them as the 'couple' and me as a kind of 'project' that both H & T undertook to save me from myself so to speak. Thus T's mother is a bit quicker to point out if I'm failing in any way yet she still is very approachable.
My mother has long since passed away and my father is very reserved in his 'speeches' so I've no idea as to his precise knowledge.
Some close friends, I would definitely say two or three, know what is going on but choose to accept it as I've been a 'work in progress' for ages now.
Sorry to go on for so long, but hope that helps.