For me it would be age and finances! I have a son who's 2 next month and my 2nd is currently overdue. I'm 33 now and 34 in october. If we did have a 3rd i'd want to wait until the first was at school because of childcare costs, but then i'd end up being 36/37 and I don't really want to be having children at that age (no offence to those who do). I think with the age gaps you will have it'll be fine. Your first will be at school, your 2nd will be entitled to their free nursery places (if they still do that) so you will have plenty of time to spend with the baby. I am the eldest of 3 - when my brother was born I was just over 5 and at school, my sister was 3 and went to playgroup. My mum said it was pretty good as we were in a routine, and she got to spend a lot of time with my brother. I have a friend who is currently pregnant with her 3rd, but she has a big age gap between the first 2 - the eldest will be 12 in Oct and the 2nd will be 2 in Oct. The 3rd is due soon. They have a 2 bedroom flat!