@ It is virtually impossible that Roger Chievre was born around 960 A.D. since his sons were involved in the battle of Hastings in 1066.
Working backwards as their likely ages of mid twenties to thirties they would have been born say 1030 -1040, and therefore Roger's marriage to Petronilla say 1010 and if married at 20 -25 tears of age would make his dob no earlier than 1080. Alternatively if William Chievre was born say in 1041 he would have been aged 25 at the time of the Battle. His father Roger would have been married say around 1016, and most likely Roger's dob would have been 996. These two variations look much closer to what was actually the case of more accurate dates.
