We sort of deal with it on both sides. DH and I both have 6 year old girls from a previous marriage and then we have a baby together.
We have primary custody of my DD and joint custody of DSD, who is with us every weekend. Both want to be with us ALL the time.
My DD doesn't like to visit her dad too much, although she is getting better with it. For a long time, I couldn't even get her out of the car. She would cry and cry. Now things are better and sometimes she even asks to stay with him longer.
DSD wants to live with us, but her bio-mom won't let her. She feels very left out and has jealousy and self-esteem issues.
We can only do what's best for them while they are here. We don't show our feelings about our ex's or say that we are glad they don't want to be with them. I always tell my daughter how much her daddy loves her and wants to be with her.....and the same for my step-daughter. Hopefully your ex shows the same respect to you.
So anyway~I don't really have any advice, I just wanted to share a similar story. I think it's normal for kids to want to be with the other parent and you can only shower them with love while they are with you. They will realize that a bigger house, doesn't mean more love.
I hope this makes sense....I'm nak.....takes forever to type!!!
Hope things work out for you.