Welcome, I'm glad you found this thread too. I am in a slightly similar situation to you in that my partner has another love who he would like to connect to our life. In my case however the woman isn't as keen as he is and this makes it a lot easier for me. We have been able to take things at a very slow pace and that has been difficult enough. After three years we are in a very good place but our life is still not connected with hers on a regular basis. I have come to accept that if that ever happens I will just have to deal with it.
It does sound to me that your situation is more lust driven than love driven, but that doesn't make it any easier to deal with for you. There is really very little you can do than be open to the feelings that come up for you and work through them with these people, one at a time.
I believe that when you truly love someone you cannot put limitations on them that stop them exploring who they are until you have thoroughly explored how
those new developments affect you.
I will keep an eye on this thread so keep communicating and I will try and help you with specific issues you may be going through. There are also a couple of other places that might help - the polymono group at Yahoo Groups and my blog www.polyamorouspeople.com
. I haven't posted for some time but I did record my whole process of coming to terms with my situation and there is probably something there that will be useful.
Good luck, and remember you are never alone in this.