yes, yes they can.

I, like onelittleprincess, was the eldest child. my first little brother came along when I was 2, that was fine, next one when I was 4, I cried, a lot, so I'm told. I desperately wanted a sister. then mum got pg again, when I was 6....another boy, I refused to go to to the hospital to see her or him, I referred to him as "it" for the first 2 years of his life, I was very disappointed and quite horrible about it all really....

but, I do now love all 3 of my brothers, still wish I got that sister though