Complex sentence: His war skills as well as ties with knights Templar are well documented because he donated lands in Bosnia and Slavonia to their Order, and his own biological brother Dominic was on record as a knight Templar.
Split into simpler sentences: His war skills as well as ties with knights Templar are well documented, as he donated lands in Bosnia and Slavonia to their Order. His own biological brother Dominic was on record as a knight Templar.