The lawyer said the court is requiring my Dads death certificate in order to settle the first wife's estate...they were divorced in 1965 and she died in 2010
If they were legally divorced, the lawyer should have no need for a death certificate unless the lawyer is trying to claim an asset. I would not give it to the lawyer and get an explanation of why it is needed.
Are you referring to a death certificate for your father? You have no legal obligation to provide this. You can ask for the cost of obtaining it to be reimbursed.