Is it permissible to give zakat to underage siblings and hand it over to them for their disposal while they are in their father's custody?

It is permissible to give Zakat to poor siblings who do not have enough to suffice them, if their father is also poor and unable to spend on them. The Zakat is to be given to their father because he is the guardian of their money, while informing him that it belongs to his children.