The Crusader who became Muslim and fought against Templars with Saladin, Robert of St Albans.
1. Robert led an Army of Muslims in Jerusalem.
David Hatcher Childress said:
“The English Knight Robert of St Albans left the Templars, became a Moslem and led an army for Saladin against Jerusalem” [Pirates and the Lost Templar Fleet: The Secret Naval War Between the Knights Templar and the Vatican page 94]
2. Robert Married niece of Saladin.
It is mentioned in the book The experience of crusading.
“Another Renegade, Robert of St Albans, an English former Templar, is said by Roger of Howden to have married a niece of Saladin.”
[The experience of crusading, Volume 2 Edited by Peter Edbury, Jonathan P. Phillips, pg.195, Cambridge University Press]
3. Robert was Martyred:
It is mentioned in the book The experience of crusading.
“He devastated the country around Nablus and was killed outside Jerusalem in 1187.” [The experience of crusading, Volume 2 Edited by Peter Edbury, Jonathan P. Phillips, pg.195, Cambridge University Press]