I think a two yr age gap is great.
I have 17mths between #1 and 2 and 22 mths between #3 and 4 and they are great friends and have always gotten on well.
There is a 4yr gap between #2 and 3 and they do not get on at all...it may be personality as well though.
There is 11mths between #5 and 6 and 13mths between #6 and 7 and that is a little to close (not that I would change it but unless you are a tad crazy I would recommend it )