I've met a fair few guys (over the internet of course) who were married guys, and self-proclaimed 'not gay', but just* enjoyed some male-on-male action...
There was one quite regular guy I met up with over a few years, until we sadly lost contact.
At first, basically he just wanted his cock sucked (something which apparently his misses wouldn't do), and as I just adore sucking cock, it seemed like we were on a winner.
He had a gorgeous big cock, if not 8 inches then very nearly so, and a damn decent girth but not so* big as to make sucking him off too* much of a struggle to get him all in.
Loverly big head on his cock, and uncut too, and he always came gallons (guessing he didn't really get 'much' of anythign at home with his whife).
Anyhow, he only* wanted to be sucked off... But I gradually worked on him, and eventually he really rather got into fucking me, and damn he always felt good inside me, of course used to suck him off too still sometimes, but once I'd gotten him hooked on screwing my boy-cunt I think he just prefered that...
And then we went and lost contact... sods law...
Another time, a few years ago, I met up with a girl, well older woman I'd met over the net, who had a strong foot fetish, and as I just adore licking, sucking, smelling feet, I was again happpy to oblige, and we got up to a few other things, and I used to give her a lot of oral too, anywhere she wanted; mainly feet, also her pussy and her breasts... Guess I'm still a bit bi really, though its been years now since I was with a woman...
Also the only woman I've ever seen squirt her cum... which is pretty damn neat; I'd get her hot and when she was about to squirt get my head in position so she could squirt her juices all over my face and chest.
Anyhow...
Where I was getting too, was that I introduced her to the sensation of having someone give her a rimming, and she did have one of the most fabulus tight litel a-holes, and I used to spend a lot of time giving it a damn good rimming... As time went by I'd spend more time on her ass than her pussy, well, I much prefer the taste of ass to pussy any day... Still got to play with, lick and suck and smell her feet too which was great, and I'd regularly orgasm with her, without having my cock touched, just as a result of having my way with her feet, whilst she tortured my nipples...
Damn... and now I remember how much I miss both of them, the guy and the girl both lost contact with a few years back..
Asides those two, I've had a few guys who I've given blow jobs too, who although it wasn't explicitly said, I knew were married, and so I guess considered themselves 'straight'... Can't say it ever bothered me, so long as they've a nice clean cock and want to unload in my mouth I'm really not bothered either way...