Communication is very important. I have been with my boyfriend for almost 4 years. His twin daughters were almost 6 when we started dating. One (K) took to me immediately, S not so much. At first it was well they are only 6 and stuff like that. The girls did not have a room at his place at first b/c his bro was living with him. When his bro moved out, we turned the bedroom into the girls' room. That helped a lot. Both were very concerned about me taking on the role of their mom. We sat them down and explained to them that I was not replacing their mom. I wanted to be their friend and be there for them. It has taken awhile but they understand now. K calls me mom when they are with us. S goes back and forth b/t my name and mom. We told them they could call me what they were comfortable with. S and I had some run ins. At first my BF took her side, until one day he saw first hand how she was treating me. He put a stop to that almost instantly. S and I still have our run ins but it is getting better. However, my BF and I have always talked about things and have been on the same page when it comes to the girls.

Sorry for the really long post. I hope it helps or makes some sense. PM me if you'd like to talk. Being the "other" woman, by that I mean the kids might see us as trying to take them from their dad, is hard.