Complex sentence: In a mortuary roll prepared at her sister's religious house, she was listed first among the daughters of William the Conqueror, and she is generally the first daughter given in lists of William's children, and thus she was probably the eldest.
Split into simpler sentences: In a mortuary roll prepared at her sister's religious house, she was listed first among the daughters of William the Conqueror. She was usually the first daughter in lists of William's children, and thus probably the eldest.