Article 424 of Jaafari Personal Status Law

If both parents survive and the deceased has no child and no husband or wife, the mother shall receive one-third of the estate as a prescribed share and the remainder shall go to the father, provided that there is no brother or sister of the deceased who reduces the mother's share. Where such a person exists, the mother shall receive one-sixth and the remainder shall go to the father. The brothers and sisters shall inherit nothing, even though they exclude the mother from the one-third share.