It's rather up to everyone engaged in sex in the room. If no one is opposed to witnessing or engaging in male homosexual acts, you're free to do what you want with the other male in the group. If not, you need to respect the sensitivities of the group.

Since you don't specifically say, I'm assuming that your SO is long term or your married. If I were in this dilemma I would first make sure that she doesn't mind if your Bi and is willing to actively participate in your male/male sexual acts. If she's OK with it, then you have no problem at home.

Similarly, you need to determine what is your relationship with the other couple. If it would be offensive to them and ruin your friendship, you need to determine which is more important to you; giving a blow job or keeping their friendship.

Whatever you do, enjoy yourself and have great sex. Even though we're often with partners that don't share a sexual interest with us; e.g., anal sex, homosexual acts, etc., it doesn't diminish the enjoyment of the overall sex.

Here's hoping this helps.

You are there to have sex, so if it fits in your mouth, put it in your mouth. If your gal is like me, the turn-on will be incredible. Have him on his back with on of the gals on top reverse cowgirl, you can suck her clit and his balls with some cock licking for good measure

If two's company, and three's a crowd, what is a foursome?

I agree with the last part of spermkiss comment. It might not turn out that way. I am courious about sucking but nothing else, I would't mind if a friend sucked on me.

I don't know about foursomes, but I had several MMF three ways. I'm about 99.9 per cent gay but when I was in my early thirties I had an affair with a woman. She knew I was gay and was totally cool with it. (Most women are.) In any event it was with her that I had the three ways.

One guy was particularly memorable because he was very reluctant to be in bed with another man, even with a woman between us. Once we got going, however, he warmed up to the idea. He got comfortable with me touching him and sucking his dick. He even began playing with my dick.

After about an hour the lady excused herself and went out to the kitchen for a snack. As soon as she was out of the room he really went on a roll. He French kissed and sucked cock like a champ. Later he told me that since he had never been with a man before and since he might not get another opportunity he wanted to really find out what it was like while he had the chance.

So if you want to suck cock while in a foursome with another couple, go for it. Most women are turned on by man-on-man sex and most men like having their dicks sucked no matter who's sucking. I doubt it will shock anyone and even if it does, they'll get over it.