 Thomas Penn's mother was his father's second wife, Hannah Callowhill Penn (1671–1726), daughter of Thomas Callowhill.Penn inherited the position of Proprietor of the Colony of Pennsylvania for the British Crown in 1718 along with his brothers John and Richard on the death of their father William Penn, until 1746 when John died.Thomas continued as the Proprietor with Richard's son, John, and his own son John Penn until 1775.