I have two girls...the first one was my idea, and the second one was actually his idea! He thought Emma needed a playmate and someone to keep her company, so we started looking around. We wanted another female-I wanted to pee pad train them both, and I didn't want to worry about a boy marking anything in the house. Also, my DH knew I'd dress up my little furbabies...he said if I was going to dress them up and do their hair, then they might as well be girls
My two are about 8 months apart in age-Emma was born in March 2006, and we got her Memorial Day weekend. Milli was born in late November 2006, and she came home in February 2007. Emma was potty trained reliably by the time we brought Milli home...I'm not sure, but I think I would have gone crazy trying to train both of them at the same time! At least now when we have an accident, we know who did it!
Honestly, I think there are pros and cons to getting them closer and farther apart in age...it will work both ways! Can't wait to see what you decide!