In documents filed today in L.A. Superior Court and obtained by TMZ, Carla Burgos Van Bastelaar, claims she is the sister of the murdered woman, Monica Burgos Beresford-Redman.
In the documents, Carla states, "The mother of the children, Monica Burgos Beresford-Redman, was found murdered in Cancun, Mexico ... Their father, Bruce Beresford-Redman, has been arrested on suspicion of murdering her."
Carla also states, "I am the nearest blood relative of their mother, as I am her sister."
Beresford-Redman was released from custody early Friday morning because investigators didn't have enough evidence to hold him.
UPDATE 9:02 PM ET -- Looks like the sister was too late. A judge has granted temporary custody to the children's grandparents. It is believed it was Bruce Beresford-Redman's parents who were given custody.