Having spent all his money, my brother is asking me for financial help. He talks to me about maintenance. What is it ? Can I free myself?

The obligation to provide support is provided to a person who is unable to provide basic necessities (housing, food, clothing). The amount varies depending on the resources of the applicant and the needs of the applicant.

She plays between parents and children and between in-laws and son-in-law or daughter-in-law (under certain conditions).

Legally, it is not applicable between brothers and sisters. If your brother is in need, you can help him (voluntary help) but this is not a legal obligation.