Pagan (Pain) Peverell, Lord of Whittington - Birth date of Pagan Peverell

Since his daughter Isabel was born about 1186, shouldn't Pagan's birth be closer to 1160 instead of 1060 that is given? I checked her husband and children, so that her date seems reasonable, but Pagan's date does not. Are there generations between Isabel and Pagan or between Pagan and his listed ancestors? Help?