cre zia ▁di ▁Cos imo ▁de ' ▁Med ici ▁ ▁( 1 4 ▁February ▁ 1 5 4 5 ▁– ▁ 2 1 ▁April ▁ 1 5 6 1 ), ▁a ▁daughter ▁of ▁Cos imo ▁I ▁de ' ▁Med ici , ▁Grand ▁Duke ▁of ▁T usc any ▁and ▁Ele on ora ▁di ▁To led o . ▁She ▁died ▁two ▁years ▁afterwards ; ▁poison ing ▁has ▁been ▁sus pected , ▁the ▁Duke ▁poison ed ▁her ▁and ▁she ▁died ▁at ▁the ▁age ▁of ▁just ▁ 1 6 . ▁On ▁ 5 ▁December ▁ 1 5 6 5 , ▁Alfonso ▁married ▁his ▁second ▁wife ▁Barbara ▁of ▁Austria ▁( 3 0 ▁April ▁ 1 5 3 9 ▁– ▁ 1 9 ▁September ▁ 1 5 7 2 ), ▁e ighth ▁daughter ▁of ▁Ferdinand ▁I , ▁Holy ▁Roman ▁Emperor ▁and ▁Anna ▁of ▁Boh emia ▁and ▁Hung ary . ▁On ▁ 2 4 ▁February ▁ 1 5 7 9 , ▁Alfonso ▁married ▁his ▁third ▁wife ▁Marg her ita ▁Gonz aga ▁( 2 7 ▁May ▁ 1 5 6 4 ▁– ▁ 6 ▁January ▁ 1 6 1 8 ). ▁She ▁was ▁the ▁el dest ▁daughter ▁of ▁William ▁I , ▁Duke ▁of ▁Mant ua ▁and ▁Ele on ora ▁of ▁Austria . ▁Marg her ita ▁was ▁the ▁nie ce ▁of ▁his ▁second ▁wife ▁Barbara . ▁ ▁He ▁had ▁no ▁known ▁children , ▁legit imate ▁or ▁otherwise . ▁ ▁Su cc ession ▁The ▁legit imate ▁line ▁of ▁the ▁House ▁of ▁Este ▁ended ▁in ▁ 1 5 9 7 ▁with ▁him . ▁