The mother has a pension from working in a riba-based bank: is it permissible for the children?
Question

His wife lives with her mother, who used to work in a bank, in the stock exchange department, and she receives a pension. Her mother refuses to let his wife (her daughter) spend anything. What should he do, as he cannot take his wife with him and he cannot leave her in the apartment on her own, when she has their baby daughter with her who is still breastfeeding?
Praise be to Allah.It is not permissible to work in riba-based banks, and the money earned from this work is not permissible, unless the worker was unaware of the prohibition, in which case he is pardoned for the money he received. That also includes payment at the end of service and the pension that was deducted from his salary. But if the person was aware of the prohibition, none of that is permissible for him.
Please see the answer to question no. 12397 .
This money that is haraam because of working in the riba-based bank is only haraam for the one who acquired it; it is not haraam for the one who takes it from him in a permissible manner. So there is nothing wrong with her daughter eating from this wealth, although refraining from that is more appropriate, especially if she offers advice and explains that riba and and the money acquired through this means are haraam.
Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) was asked: My father – may Allah forgive him – works in a riba-based bank. What is the ruling on our taking anything of his income and eating and drinking from his income? But we have another source of income, which is through my older sister, who is working. Should we stop taking maintenance from my father and take our maintenance from our older sister, noting that we are a large family, or is there no obligation on my sister to spend on maintenance, and should we take our maintenance from my father?
He said:
I say: take your maintenance from your father, and you may enjoy it whilst the sin of that is borne by him, because you are taking the wealth from your father lawfully, for he has wealth and you do not have any, so you are taking it lawfully, and if the sin and consequences of that are to be borne by your father, that does not concern you. The Prophet (blessings and peace of Allah be upon him and his family) used to accept gifts from the Jews, eat the food of the Jews and buy from the Jews. Even though the Jews are well known for dealing in riba and consuming unlawful wealth, when the Prophet (blessings and peace of Allah be upon him) accepted these things, he did so  in a permissible way, and if something is acquired in a permissible way, there is nothing wrong with that. For example, look at Bareerah, the freed slave of ‘Aa’ishah (may Allah be pleased with them both): some meat was given to her in charity, and the Prophet (blessings and peace of Allah be upon him) came into his house one day and found the pot on the fire, so he called for some food, and food was brought to him, but there was no meat in it. He said: “Did I not see the pot on the fire?” They said: Yes, O Messenger of Allah, but it is meat that was given in charity to Bareerah – and the Messenger (blessings and peace of Allah be upon him) did not eat food that was given in charity. But he said: “It is charity for her and a gift for us.” Then the Messenger (blessings and peace of Allah be upon him) ate, even though it was haraam for him to eat food that was given in charity, because he did not receive it as charity; rather he received it as a gift.
So to these brothers we say: Eat from your father’s wealth and enjoy it, even though your father with bear the sin and consequences thereof, unless Allah, may He be glorified and exalted, guides him and he repents, for whoever repents, Allah will turn to him in mercy." (From al-Liqa’ ash-Shahri  45/16).
And Allah knows best.