Johnnie walks into his parent's bedroom and see's his dad giving his mum one, his dad just laughs, throws a pillow at him, shouting "Get out!".
A little while later, his dad hears a commotion coming from inside Little Johnnies bedroom, he rushes in only to find Johnnie shagging his gran.
Johnnie looks at him and says
"Not so fucking funny when it's your mum is it?"...........

These jokes of yours are very close to the bone...but they do make me giggle