My brother is 2 years younger than me. We are pretty close. (SIL is great & we all get along really good, so it helps ) My sister is 6 years younger than me, 4 years younger than my brother.

TBH she's a PITA...but not because of her age. More because of her selfishness & immaturity. She's starting to get better, but turning the music up when my 2 week old baby just went to sleep in the same room, then telling me that I should go home is a bit much. Turning the TV up over mum & dad's conversation with another couple in the same room. Maybe ok if she was 6! Not 19!!

I decided on 3 years between mine coz MIL had 3 years between her youngest 2. OK for boy/girl, but my girls don't get along near as good! I hope they do when they are older.

5-6 years should be ok As everyone else has said, its more the personalities than anything.