No self control... where does it come from?

My dad has adult onset diabetes - which was diagnosed a dozen years ago. He had a heart attack several years back because he wasn't taking care of himself. And he still doesn't. I watch his weight creep up and down. I watch him eat the cookies and other sweets he should really stay away from. I watch him raid my candy jar (the one I don't even go in) every time he comes over to my house. I'm really thinking about hiding that jar. I can't stand it... I can't stand watching him not take care of himself. But I have the same lack of self control. I wonder if there's anyone in my life that watches me self destruct... watches me take that cookie and brownie when I really should be reaching for the strawberries or carrots.