H.A.
J.,
My sister and I are close, I lived with her when she went through a bad divorce and this is the second marriage for my husband, so I think I can understand you a little bit. I would encourage you to get counseling, it will help you deal with this change in your life. It will seem like a second adolescence to the both of you. And you will need to help your children get through this too. Of course a group of single friends will help a lot too. My grandma used to say: Even though it is hard now... this too shall pass.
And you will find another partner to share your life with. So, do not despair.