I agree with the financial risk .... I currently have TWO SETS of siblings so each making up 40% of my income and than one single kid .... come September I loose one set to school FT but the other will be 'splitting' with the youngest staying and the eldest going off to big school.

As for behaviour ~ siblings depends solely on the personality of them ~ I currently have one set I could do with out cause they bicker and fight and act like siblings ALL DAY LONG and another set where they are an awesome support to each other when needed but able to play and go about their thing.

The fact is that the behavior of mothering, feeding off each other, fighting and other issues can just as easily occur with ANY set of kids they do not have to be related for those things to happen I have had little girls who 'baby/mother' the younger children all the time and yes it is annoying constantly having to say 'let Johnny be ~ he needs to learn to do that for himself' or 'Little Sally is not a doll for you to be picking up and carrying around' and so forth.