So, some back story. I (31F) am in a relationship that is currently monogamous. My fiance (41M) has always been firmly monogamous, and did not think it was possible for him to become interested in anyone else. I, on the other hand, have generally always been in open relationships, until this one. So to me, monogamy is abnormal, and I don't exactly expect him to never be attracted to other women, if that makes sense.

I have a close friend who I invited to live with my fiance and I as she was fleeing an abusive relationship and had nowhere safe to go. So you can probably guess where I'm going with this lol. My close friend and I have a ton in common, and unexpected to him, he developed a crush on her. I saw it coming from a mile away, but it completely side-blinded him. It's pretty much made him question his whole reality. I've talked to him a lot about how even tho we agreed to a monogamous relationship, I don't fault him whatsoever for having these feelings and I'm not mad, that I want to work together to make sure everyone's needs are met in a safe way.

My close friend also has revealed that she has also developed attraction, for both of us, and really wants a 3some. However, she feels very worried that it will harm our relationship and harm our friendship, and that we would kick her out over it. I've reassured her that this situation is non-threatening to me and we have every intention to allow her to stay here as long as she needs.

My fiance and I have had a lot of conversations about it all. I have told my fiance that I have worked hard to change my way of thinking about relationships to be monogamous, and I can't really just turn it off like a switch. However, I am not jealous or otherwise threatened by the situation, and I am open to doing some experimenting, but we need to tread carefully and slowly, because this can easily go really badly.

When he first opened up about his emotions and saw that I was accepting of the situation, he got really excited (horny) over the idea of having a 3some. He's never had one before. But I told him, we need to give it some time. I'm not entirely opposed, but we need to have a "clothes on" conversation about it all together. We need to let the excitement die down a bit first because getting too lost in the exitement is how this situation could become destructive and damaging. Since then, he's definitely calmed down some and started thinking about how it could affect all of us long term.

We've talked a bit about boundaries. I've told him that I wouldn't be opposed to some oral play, but I don't think it would be a good idea for him and my friend to have PIV sex at this time. I also have told him I wouldn't be comfortable swapping too many fluids. Told him I think he is thinking with his dick a bit too much, and she is too vulnerable from her ex. He fully agrees with me, but we both think it would be unrealistic for oral to not progress to PIV sex, so we've been trying to think of a way to keep everyone on track and keep it fun and light.

I haven't brought it up yet, because I know my fiance would get too exited about it to think clearly, but I am considering allowing them to do some anal. My fiance LOVES anal and my friend also has a kink for anal. I, however, have a chronic intestinal illness and it's just something I can't really offer him. Im not sure tho if that would be taking it too far.

Something else that is probably an important detail is that she definitely is still also seeking her own relationship. Our goal is not to become a triad. She really needs her own primary partner and we don't want to trap her in some sort of unicorn situation. However, there is a lot of interest in having some periodic non-monogamous experimentation and I am open to facilitating that.

They both have pretty much has given me full authority over this situation since it's not new to me, and entirely new to them. I feel like I've got it pretty well under control, but these situations can easily get tricky. Thoughts?