I am eldest of 3 and it was fine growing up. There is 19 months between myself and 1 brother and then 8 years between him and next brother (so 10 years between youngest and oldest).

My best friend has 3 kids and loves it (well most days) she has a 3 year old, 2 year old and a 7 month old. Oldest 2 play well together (well as good as toddlers do and always interetsed in ther brother.)

Good luck