False.
I can't comment about boys, because all my nuts seem to be able to produce is girls and blueness, but I know a little bit about girls. My oldest is much like most of yours; she is all girl, loves to cuddle, read, hang out with me, etc., but my next little girl couldn't be any farther away from her sister in pretty much every facet of life. First of all, they don't look alike. At all. Oldest is tall, skinny, petite, with long straight brown hair. #2 is a short, stumpy, THICK grump of a thing with a damn near white curly mop on top. My oldest is nice, loving, and unbelievably caring, while #2 seems to go out of her way to be rude or make others feel bad. #1 is a social butterfly, makes friends at any/all venues from shopping malls, doctors offices, church, etc., is a voracious learner and can't get enough reading, learning, or experiences. #2 wants to sit on her *** with an Otter Pop and the iPad, in seclusion, behind the back side of her bed where nobody can see her or bother her. She has zero manners, is not polite to anyone, waits for her sister to make something pretty, just so she can stomp on it, tear it up, or destroy it as quickly as possible. #1 wouldn't hurt a fly, while #2 is all about death, destruction, chaos, and violence.
In short, I don't think gender has much to do with it. I have no idea how my girls could be so polar opposite of each other, but it sure sucks. #2 is going to have a very hard life, which is hard to think about as a father, but she's 5 and has gotten progressively worse as the years roll by. #1 might discover the cure for cancer, life on another planet, or the missing link -- and I wouldn't be a bit surprised.
Boys are stupid.
I lol'd because I always knew.
And the majority of them are underage, no doubt.