Thomas was the son of Sir Robert Newcomen, 4th Baronet and Anne Boleyn.
He was an adherent of James II of England following the Glorious Revolution, and was Colonel of Newcomen’s Regiment of Foot during the Williamite War in Ireland.
[1] He was killed in fighting near Enniskillen at the Battle of Newtownbutler in 1689.
He was succeeded in the baronetcy by his son by his second wife, Robert Newcomen.
[2][3] His daughter, Catherine, married Simon Luttrell.