This question deals with two topics:
1 – The ruling on giving zakaah to parents.
Shaykh Ibn Baaz (may Allaah have mercy on him) said: “The Muslim cannot give his zakaah to his parents or to his children; rather he has to spend on them from his wealth if they need that and he is able to spend on them.”
From al-Fataawa al-Jaami’ah, vol. 1, p. 306
2 – Giving zakaah to one’s siblings. Please se Question No. 22177.