Marquess Of Dorset John Beaufort
John was born in 1373.  He died at the age of 37 in 1410.

 Margaret Holland
Margaret is no longer alive.

 Earl Of Somerset Henry Beaufort
Henry was born in 1401.  He died at the age of 17 in 1418.

 Duke Of Somerset John Beaufort
John was born in 1403.  He died at the age of 41 in 1444.