Your old teen mom would never understand how you feel about wanting to "share" the penis with your teen girlfriend. Old enough to know better, she was raised by her Mom's, who didn't seem to mind if mom shared the shaft with her. She got that big cock when she turned thirteen and you were old enough to know better, but still your teen did it anyway. I know it makes you angry and frustrated as an adult, but there is a very simple solution. Mom can't be too proud to admit it, but now you too can have a big penis even if she doesn't want you to.