All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
Paying Zakaah to brothers or sisters is lawful according to the prevailing opinion of the Muslim scholars, especially if they are needy or poor. It is even desirable according to the following Hadeeth. The Prophet said: “Giving alms (Zakaah and others) to needy people is rewarded as alms only but giving them to a needy relative is rewarded both as alms and an act of keeping ties with kinship.” [An- Nasaa-i]
So, if you have needy brothers or sisters who do not have anyone to care for them (a son, a husband or whose father is poor himself) there is no harm in your giving them your Zakaah. It is even desirable as mentioned earlier. They are eligible to receive Zakaah even though the husband or father is alive as long as they are poor and don’t have what to spend on themselves.
Allah knows best.