Yes, it is allowed to help any family member from Zakat if he is: 1) Really poor.
2) Abiding to Islamic rules.
3) He should not be a parent or a spouse or a sibling, because it is compulsory to look after the needs of your parents and spouse and siblings from your own money not from Zakat or Khums.
You don't need to inform him if he is entitled to Zakat that it is from Zakat.
It is highly recommended to help the needy relatives as the Hadeeth says: There is no charity when a relative is in need. لا صدقة وذو رحم محتاج.