keep the money that belongs to your sister's (Part No. 14; Page No. 245) children which was assigned to them by the state. You are only permitted to take from it what is necessary, and give the rest to them when they come of age. You should also pay the Zakah of the money on their behalf. If you trade in this money or give it to a trustworthy person to invest it on your behalf, it will be even better. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.