 John was the youngest of the four sons of Erard II , Count of Brienne , and Agnes of <unk> . He seemed " exceedingly old ... about 80 " to the 14 @-@ year @-@ old George Akropolites in 1231 ; if Akropolites ' estimate was correct , John was born around 1150 . However , no other 13th @-@ century authors described John as an old man . His father referred to John 's brothers as " children " in <unk> and mentioned the tutor of John 's oldest brother , Walter III , in <unk> ; this suggests that John 's brothers were born in the late <unk> . Modern historians agree that John was born after <unk> , probably during the <unk> . 
