Well between me and my brother there is just under a 3 year gap, when he was a baby my mam said it was great as i'd care for him and snuggle with him, as soon as he hit 3 or 4 the trouble began. Basically we fought...alot. And I remember me at 16 years of age and him at 13 standing at the bus stop waiting for the school bus arguing and hitting eachother

We get on abit more now, but we still have arguements.
I think if you have a bigger age gap, like 8 years (taking this from an example of my friends) the older child will definatley respect the younger one more and vice versa and you'l have a lot less problems with fighting etc.
But i suppose it just depends on family to family...