Unless it is genetics, submissive peeing is normally caused by the puppy being over-stimulated.

A good example is, I walk through the door from work or shopping and I am already feeling guilty I had to leave such a young and cute puppy alone for such a long period of time. With all the guilt rushing I greet my puppy with lots of love, hugs, kisses, and animated tone of voice. This makes my puppy very excited and stimulated. A young puppy just cannot control its bladder because the bladder is a muscle and with young puppies there is not much muscle control.

To control submissive peeing, do not make it an event when you get home. Do not use an animated tone of voice. Instead stay very calm.

If the puppy is in the house, immediately take it outside and then give the command to go potty.  When the puppy is outside, use a more animated tone of voice and greeting. A good idea in the beginning is to start interacting with the puppy outside so it can go potty first. This gets the puppy used to this routine and reinforces the behavior that the puppy should go to the bathroom outside, and not in the house.

If submissive peeing is not addressed immediately, submissive peeing in the house will make it much more difficult to house break the puppy, because the scents will be all over the house. Having these scents in the house tells the puppy it actually should pee in the house and pee in the areas that it peed in before. To correct this, behavior modification training is required.