Are children held accountable for their father's failure to pay Zakat al-Fitr on their behalf, and is it permissible for a girl to pay it for herself?

If the father was obligated to pay zakat al-fitr on behalf of his children who do not possess the means to pay it themselves, then he incurs sin if he was aware of the ruling. The zakat al-fitr for those years remains a debt upon him that he must pay. If the children wish to assist their father by paying it on their own behalf, this is permissible provided they inform him before paying it so that the intention is formed. As for the children who are obligated to pay zakat al-fitr because they possess the means to do so, they must hasten to pay it on their own behalf.