Elisabetta Gonzaga
Because her husband , Duke Guidobaldo da Montefeltro , was impotent , Elisabetta never had children of her own , but did adopt her husband's nephew and heir , Francesco Maria I della Rovere . 
<triplet> Guidobaldo da Montefeltro <subj> Francesco Maria I della Rovere <obj> relative <triplet> Francesco Maria I della Rovere <subj> Guidobaldo da Montefeltro <obj> sibling