Whose maintenance is Islamically obligatory?

It is obligatory to spend on one's wife and children. The wife's maintenance is obligatory even if she is wealthy, while the children's maintenance is obligatory under two conditions: their poverty and inability to earn, and that the father's maintenance is in excess of his needs. It is also obligatory to spend on poor parents if the son is wealthy. As for other relatives, such as brothers and sisters, their maintenance is obligatory under three conditions: their poverty, the availability of surplus wealth beyond the needs of the provider, and that the provider is an heir.