I think the girls might love having a little baby brother or sister. Just try to include them and emphasize how they will be wonderful big sisters. I was worried my 14 year old daughter would be jealous of a baby in the house. She has always been mommy's little baby. Turns out her maternal instinct kicked right into gear and she absolutely loves having a baby brother. She is not jealous at all of him. Just do your best to make them feel included with the role of big sisters.