I'm not dealing with this personally but a friend of mine is. She and her partner both have kids from previous relationships but they don't seem to have trouble with it because the kids are very involved, they love spending "family time" with them.
I did not have kids before, however my husband did. There is not an issue now however since we have an age gap, 19years. I am closer in age with the children. His son has an issue with me. In fact it caused some issues one day. There is not an issue anymore. This is because his son refuses to talk to him.