Sister-in-laws

I wouldn't feel comfortable if it was my husband or wife. In a group situation maybe but not one-on-one. Too easy for something weird to happen accidentally.

Trust your instincts.

I guess it would be similar for any other friend. Either you trust him, or you don't.

I have close male friends and mu husband has close female friends. (In fact, my "Maid of Honor" was a "Man of Honor" and his "Best Man" was a "Best Woman".)

Since we've been married, he has visited this friend once alone. (It was to be with her for her husband's funeral.)
Another time, my male friend visited me when my husband was out of town. (Due to a scheduling fiasco.) Neither time did either of us have any issues.
My husband recently got in touch with a woman he dated 18 years ago, in high school. He had not spoken to her at all in that time (it was a bad breakup) and often wondered whatever happened to her. And was excited to tell me about finding her, and learn about her kids and stuff. He was also sad that she told him "I only want to exchange email, though, and I don't want my husband to know I've talked to you." I mean, she's been married to this guy for 20-some-odd years now. Shouldn't that count for something? And my husband thanked me for not being "the jealous type".

So, my advice is trust 100% - jealousy, especially unfounded jealousy, can wreck a relationship. If you can't trust them, it almost doesn't matter whether they are cheating or not, because the doubts alone will drive you nuts. It's all-or-nothing in my book. And if you accuse someone of something they didn't do, ironically, they are more likely to do it in the future. ("I may as well, because I'm getting blamed for it anyway.") Jealousy is indeed a green-eyed monster - banish the thought.

On the other hand, I'm also convinced that I would know if there were a real affair. My husband can't get away with stealing so much as a cookie from me, so I don't think he would be able to keep a real secret from me, so maybe that's my confidence speaking.

And when I say "all or nothing", I do mean that if I ever find any reason that I can't trust him 100%, I won't be able to continue the marriage, period. And deep down, he probably knows it.

Good luck.

Um, your husband and your sister? Or you and your brother-in-law? I've had a couple of times that I've taken my daughter out with my niece and brother-in-law. I'll admit, I felt weird when people would just assume we were a family but, as long as my husband and sister are fine, I guess the situation's okay. It's family.

Or are you talking just the adults hanging out without the kids? I think that's different. Maybe every once in a great while -- maybe --, but I wouldn't want my husband doing one-on-one hanging out with another woman on a regular basis regardless of who she is.

Getting married kinda implies no more going on dates with other women -- maybe he needs a reminder? (If he argues, "It's not a DATE!", here's the definition of a date: a social appointment, engagement, or occasion arranged beforehand with another person: to go out on a date on Saturday night.)

Doesn't sound good. Why are they doing activities without their own spouse????

If it doesn't feel right, then its not right for you/yours. Trust your heart.

alone? not appropriate...not even if they are "just freinds" it raises questions and there really is no need for it - the opposite sex campanion for a male is his wife and visa versa...

Really it just doesn't seem necessary. So many things could happen whether they planned it to or not and it just doesn't seem worth the risk. You don't have to be jealous to want a secure relationship. Just try to avoid the risk that something potentially relationship fatal could happen. What I am saying is, there is no need for one on one time with the opposite sex if it is not your spouse or your own family. With everything that could potientially happen, it just seems too risky. Good luck.