Sheikh Hânî al-Jubayr, judge at the Jeddah Supreme Court
The financial obligations that a person has to his brothers and sisters falls under the general ruling of support for blood relations who are not a person’s parents, grandparents, children, or grandchildren.
Support for such relatives is only obligatory upon a person when the following three conditions are met:
1. The one providing the support is determined by Islamic Law to be an heir of that relative, meaning that he is entitled by Islamic Law to receive a prescribed share of inheritance from the estate of that relative in the event of that relative’s death. Allah says: “And upon the heir is a like duty.” [Sûrah al-Baqarah: 233]
2. The one receiving the support is in poverty and is unable to earn a living. If the relative is perfectly capable of earning his own living and simply refrains form doing so, then it is not the duty of his heirs to support him on account of his own negligence.
3. The one providing the support must be financially capable of doing so. If he is poor, he is not obliged to provide support for his brothers, sisters, and other more distant relatives.
When these conditions are fulfilled, the person’s responsibility to support his relative will be commensurate with his prescribed share of inheritance. The other heirs of that relative will be responsible to provide the rest.
[For example, if a certain person is entitled to inherit an eighth of his relative’s estate, then his legal obligation towards that relative is limited to providing one one-eighth of that relative’s needed support. That relative’s other heirs, in turn, will be liable to contribute towards that relative’s needs accordingly – Fatwâ Department]
And Allah knows best.
Source: Islam Today