I have one sister 10 years younger & one 4 1/2 years younger & am quite close to both, although I left home at 16 so wasn't with my youngest sister very long. I also have a brother who is 20 years younger than me (he is 4mths younger than my DS1!). Now that's a gap!

I wanted to have mine close together, DD1 & DS1 are 2 1/2 years apart... they don't really have much to do with each other though, they only really did when they were very young & before DS2 came along. I think gender has a bit to do with that... the 2 boys do more together (of course that means they argue more too! )

Now we have DD2, she is 7 years younger than DS2 and everybody of course adores her.. that is one benefit of a bit of a gap, much less rivalry & jealousy, they see her as a gift, not competition. And they are quite helpful to have around too

I think - just IMO - you are better off to work out when it suits you rather than worry about the gap. 5-6 years isn't too much, and as with my first two, even if you have them closer there's no guarantee they'll get on, kwim?