Assuming said genitals have not been mutilated by your loving owners. When it comes to reincarnation I tend to only want to come back as an animal that does not regularly have bits of its genitals cut off to fit in better with humans.
Most humans are wankers. I'd rather be a dog - don't have to work, you can sleep all day if you fancy it, and go for nice walks every day. And you can lick your own genitals.
first they were born a Human rather than a slug or ferret