Is it permissible to give zakat to two brothers who need it to build and expand their homes in their father's house?

If your two brothers are poor and their dwelling is not sufficient for them, it is permissible to give them Zakat (definition) to enlarge their dwelling, provided that the Zakat is given into the ownership of the deserving recipient, who may then dispose of it as he wishes. If he then gifts some of it to your father or builds in your father's house with his permission, this does not harm the one who paid the Zakat, as long as he has given its ownership to its deserving recipient.