Short answer
Their share still belongs to them. It became theirs the moment the first person died, so it passes on to that heir's own heirs as part of their estate. Scholars call this munasakha. Divide the first estate as if they were alive, then divide their share among their heirs.
An heir who survives the deceased, even for a moment, owns their share at the time of death. If they die before distribution, their share joins their own estate and is divided among their heirs (munasakha), after their debts and bequest. Their spouse and children may thus receive part of the first estate.
The four schools agree on this.
Explanation
In many families, property is left undivided for years. A grandfather dies, then one of his sons dies, then a daughter, and the family no longer knows who owns what. Islam has a clear method for this.
The principle. Inheritance happens at the moment of death, not when the money is shared out. So anyone alive at that moment becomes an owner of their share, even if they die a day later. If they die before receiving it, their share is now part of their estate.
How to work it out:
- List the heirs of the first person who died, including those who have since died, and give each their share.
- Take the share of the heir who died later, add it to everything else they owned, and pay their debts and bequest from it.
- Divide what remains among their own heirs, who may include a wife, children or parents who were not heirs of the first person.
- Repeat for each later death, in order.
An example. A man dies leaving a wife, a son and a daughter. Before the house is sold, the son dies, leaving a wife and a small child. The son's share of his father's estate goes into his own estate, so his widow and child now own part of the grandfather's house too. Leaving them out would be taking their right.
If two relatives die together and it is not known who died first, such as in an accident, neither inherits from the other; each estate goes to their living heirs. These cases get complicated fast, so ask a mufti to do the calculation, and use the inheritance calculator for each stage. Better still, divide estates promptly; see delaying division.
Ask a mufti about your own case. This answer explains the general ruling. When the details of your situation matter, as they do here, ask a qualified mufti and give them the full facts. Where to ask a scholar.
The evidence
Quran, Surah An-Nisaa 4:7
لِّلرِّجَالِ نَصِيبٌۭ مِّمَّا تَرَكَ ٱلْوَٰلِدَانِ وَٱلْأَقْرَبُونَ وَلِلنِّسَآءِ نَصِيبٌۭ مِّمَّا تَرَكَ ٱلْوَٰلِدَانِ وَٱلْأَقْرَبُونَ مِمَّا قَلَّ مِنْهُ أَوْ كَثُرَ ۚ نَصِيبًۭا مَّفْرُوضًۭا ﴿٧﴾
For men is a share of what the parents and close relatives leave, and for women is a share of what the parents and close relatives leave, be it little or much - an obligatory share.
Each heir has a share that is theirs by Allah's decree.
Sahih al-Bukhari 6732
Sahih... ألحقوا الفرائض بأهلها فما بقي فهو لأولى رجل ذكر ...
"Give the fixed shares to those entitled to them, and what remains goes to the nearest male relative."
Each estate is divided by its own heirs at the time of death.
Where the ruling is recorded
- al-Sirajiyya with its commentaries, Bab al-Munasakha. The method for an heir who dies before division.
- al-Fatawa al-Hindiyya, Kitab al-Fara'id, chapter on munasakha. Calculating successive estates.
- al-Durr al-Mukhtar, Kitab al-Fara'id, section on those who die together. Those who die together do not inherit from each other.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.