I'm 41 and my biological father died at 42 after a long time exposed to Agent Orange. My Pop, who raised me, is now 73. No genetics are shared between my Pop and I, he decided to adopt me when I was 6 months old.
I don't think Pop expected to live as long as he did, nor did my biological father expect to die as young as he was. Given these facts, as long as I outlive my biological father, everything else is gravy...