Your instincts are right, I would be very leary of being too close to them. Personally I wouldn't want to be around them AT ALL, but thats me. If DH wants to stay friends, great. They aren't your friends and if you feel iffy at all about them, then you have every right to not be around them. Try to explain to DH that he wouldn't want to be hanging out with your Ex's best friend either. The shoe on the other foot usually gets the point across.

okay, my DH "had" a friend. I NEVER approved of him, that is a known cocaine user - he failed his life insurance test because he tested positive for drugs in his blood stream - is 'in' with the BM.

STAY AWAY FROM ANYONE THAT TALKS TO BM. That includes her family.

Are these friends that your DH and his ex aquired together or were they your DH's friends before he met BM? The answer to this question does make a difference to me and my advice.

If they became friends while married, I would totally feel the same as you.

Now if they were DH's friends before he got married, they more likely will be more true to him AND the woman who they can see makes him very happy. I know it is hard to put the wall down knowing that BM is friends with the wife, but without revealing too much about your personal life, I would continue to make an effort to have them get to know the real YOU.
I say this from experience. One of our best friends who went through a nasty divorce and then a few "serious" girlfriends before getting married again would bring the woman he was getting serious with and we were able to see things that he couldn't or wouldn't see because "he was in love"! Most importantly, we are a close group of friends and our loyalty was with our friend who we sincerely care about. Even though a couple of the women in our group kept in some contact with his ex wife, that was very guarded and eventually dropped altogether once he married his new wife. We could all see how good she is to him and how genuially happy they are together.

Ah, been there...yes, it's a sad situation...I get it that he might have friends that he doesn't want to part with just because you broke up with your ex...but really, how would HE feel if the tables were turned? I always do that with everything in my life.

DH and crazy witch were friends with a guy DH worked with and his wife. Of course, once DH and crazy witch divorced, DH stayed friends with the guy and I am 99.9% sure that the girl stayed in contact with crazy witch. DH really wanted us to be friends and I really tried. That was until they thought it was just so darn cute, in the middle of a party they were having, to show videos of parties they had had. And well, I was about 6 mos pregnant and there it was, in full for EVERYONE at the party to watch, "DH and crazy witch at their house with SKID at around 6 mos old"...I almost PUKED and literally, got up and walked outside. A few people were in SHOCK they would be so stupid, a few thought it was an innocent mistake, but really, at the end, the guys wife said "well, it's no big deal, they are no longer together...what's the problem?" Of course, that was the last time I visited them. They did come to our home once or twice after that, but DH then realized that sadly, if he wanted to have a relationship with ME, then he needed to make a choice. It was not fair to ME to have to constantly put up with such crap or be worried about what they said or didn't say to BM. By the way, at the time, we were having MANY problems in our relationship because of BM. Amazingly enough, once we stopped seeing them, our relationship GREATLY improved.

Your DH needs to determine what is most important to him, you or his friends. It is what it is and well, not every friendship in this world is meant to last forever...that's the way it goes.

PS - DH also worked with the guy, but eventually got a different job...which obviously is not always possible...but while working at the same place, then we just began doing DIFFERENT things, etc. DH could still talk to the guy at work, etc. but he understood that he should really not talk about US...by the way, guys are MUCH better than women...I think DH's friend understood that if he told his wife about stuff we did/didn't do, she'd tell crazy witch and he was very respectful of that

PS - by the way, I have a friend who broke up with his spouse some years back. My DH and I were GREAT friends with both. We of course DEARLY missed our other friend, but we loved/respected BOTH our friends. Eventually that friend remarried and we have ALWAYS treated our friend/new spouse with the same respect we'd like others to treat us. Not once have we brought up the name of the ex, or talked about the good times the 4 of us had, etc...NEVER, NOT ONCE. So it CAN be done, but I think again, if the person CAN'T do it, then they truly are NOT your friend.

Actually we have another set of friends of broke up about a year ago after 20+ yrs together. We still talk to BOTH of them. We see them SEPARATELY. Of course, each will give us THEIR side of the story, we have supported them through the break up, we tell them what they need to do to PROTECT themselves, but we always make it clear that protecting yourself is NOT hurting your EX. And even when they have tried to get out of us if we have seen the other party, we always tell them, that we love them and that is not something we will discuss. That we value their friendship and would never be the ones taking things between one and the other. They both are very thankful and our relationship is as good as before.