If someone is already legally dead, can you go to jail for killing them?

I buried my brother in 1991. Now I have a letter from someone claiming to be him demanding a share of my father’s estate. If I have the proof in my hand that he has been legally dead for over 20 years, can I be charged with killing him if he shows up at my door?

I would prefer to let the law handle it, but if he contacts my mother all bets are off.