Is it permissible for the family to eat from the zakat that reaches the sponsored orphaned nephews, with the fear that this may be unlawful?

The money that reaches orphans from Zakat, charity (sadaqah), or gifts is their property, and the rulings applicable to their original wealth apply to it. It is not permissible to dispose of it except for their benefit. Although Islam has emphasized the sanctity of an orphan's wealth, it has permitted mixing with them and dealing with them for their benefit and to bring joy to them.

Therefore, it is permissible to eat from the orphans' money that reached them through Zakat, even if the one eating is wealthy, based on the Hadith of Barirah.

It must be noted that an orphan is a child whose father has died, and the description and rulings of an orphan do not apply to someone who has reached the age of maturity.