Mother inherits from their children and grandchildren as primary heirs under Islamic law, which you may not find in many other secular or legal laws. Muslim Mother inherits one-third (i.e., 1/3) fixed or prescribed division if no Children or no Grandchildren how low soever survive, as well as if no Multiple full or no Multiple paternal or no Multiple maternal siblings survive.
Mother inherits one-sixth (i.e., 1/6) in the presence of children or Grandchildren how low soever, or if Multiple full siblings, paternal siblings, or maternal siblings survive. Mother inherits one-fourth (i.e., 1/4) if she only survives with Father and Wife. The mother's share can vary in certain conditions due to the decrease or increase of total shares under the Radd and Awal (or Aul) scenario. Refer to "Islamic inheritance sharers and residuary" to learn more.
If Husband left with Wife or Widow, Husband's parents will be eligible to receive a portion. If Wife left with Husband or Widower, Wife's parents will be eligible to receive a portion. This feature is unique under Muslim succession law; you may not find many other laws.
There is certain Hajb (i.e., blocking or exclusion) rules that are applicable for ascendants of Mother. Mother under Islamic inheritance law cannot be blocked by any inheritors, but Mother blocks Mother of Father and Mother of Mother.
The Mother can also own lifetime gifts (i.e., Hiba) from their children without any classification or restrictions.
Wassiyyah's course in Muslim succession law can give you more insight that you may consider signing up. We encourage you to read islamic inheritance book, which includes exclusive details about Islamic inheritance sharers, shares, residuary, and distant kindred relatives.