All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
Before distributing the estate among the heirs, the debt for which the deceased is liable should be deducted, because the debt has the priority over the right of the heirs in the property. After the debt is repaid, the heirs should divide the remainder among themselves according to the way stipulated by Sharee’ah.
It is not clear to us what you mean by “the deceased wife’s share”, but you should know that if a wife died before her husband, then it is her property which should be inherited and she is no longer one of his heirs; and if she died after him, she is one of his heirs and her share should be given to her heirs.
However, if one dies and leaves a mother, two sons and two daughters, and no other heirs, his mother gets one-sixth, due to the existence of the children of the deceased; Allaah The Almighty Says (what means): {And for one's parents, to each one of them is a sixth of his estate if he left children.}[Quran 4:11]
The remaining amount should be given to his four children by means of Ta’seeb (by virtue of having a paternal relation with the deceased and not having an allotted share, so they get what is left after the allotted shares have been distributed); the male twice the share of the female, in compliance with Allaah's statement (which means): {Allaah instructs you concerning your children: for the male, what is equal to the share of two females.}[Quran 4:11]
Thus, the estate should be divided into 36 shares: the mother gets one-sixth, i.e. six shares; each son ten shares, and each daughter five shares.
Allaah Knows best.