I have three step-daughters that DO share a bond, but fight like no tomorrow. They're close in age, into the same things, and smart as all get out - but there's the inherent cattiness of girls that I somehow just don't relate to even though I'm, obviously, female. Even as a child I tended to gravitate more towards the boys than the other girls because I found them to be more chill and relaxed about things and, as mentioned, a lot less catty. That could be because I grew up in a sport where it was very easy to knock another person for their equipment or lack thereof and it was literally "my horse is bigger than your horse so neener!" type of crap.
That being said, I love my son. He cracks me up, but I think (and sort of hope) that this baby is a girl given that this is likely my last as hubby is turning 40 next year and would like to retire at some point