What is "normal" touching?

I have an (almost) 8 year son.  The way he touches me, his dad and his sister are of concern.  I am wondering what is "normal"?  He seems to be masturbating on us, and more so his dad that anybody else.  He rubs his penis on us, he rubs his hand all over us.  I have caught him pressing his penis up against his younger sister many times also.  He is always wanting to rest his penis on us by hooking legs over us or laying on us.  Its makes us all extremely uncomfortable.  We have had many conversations about the way he touches and how it makes us feel.  We have shown him how to give us a hug or cuddle.  what is "okay" touching and what is not?  I have asked him if someone touches him this way but he says no.  I've asked if he want to know more about the difference between boys and girls and adults, though he doesn't seem to be interested.  I'm concerned he may start this inappropriate touching with his peers at school which will most certainly cause trouble.  When he is told to stop doing something e.g. chasing people or jumping all over people or lying on people he doesn't stop, he keeps going, to the point where I've had one child's parent ring me to tell me he wont stop chasing my daughters friend all around the school.  He is a very intelligent young boy and excels in all his classes and shows no signs of any other problems.  So is this "normal"? Will he grow out of it? Do I just continue to keep showing and telling him what is okay and what is not?  I do understand child masturbation is normal, but he doesn't seem to understand that its NOT okay to do it with other people.  Am  over reacting?

[Liquid4444]

It is normal for a boy to masturbate. It is not normal to do it against parents or siblings.:)