Stepfamily Association

I have been a SM for nearly 7years now, and now have 2 gorgeous children of my own. What I want to know is, how did your Step kids react or change when your own children came along?? My SS is an amazing young man, and does very well with my 2 kids, he is a typical brother, and they fight and tease and all those other sibling things, but he loves being their big brother and teaching them new things etc. SD has always taken on a very motherly roll with both BS & BD, loved to read stories to BD when she went to bed, always wanted to put BS to his cot, and change his nappy or get him dressed. BD is 4 and BS is 1, and recently SD has changed with them both. She is OVER affectionate with BD, and very bossy with her. and BS just seems to be in the way. I love my SK's as much as my BK's, but if they can not get along I dont know how I will cope.. Love advise or thoughts from other SM's!