Is it permissible for children to receive their deceased parents' pension while the eldest brother is prevented from receiving it due to exceeding the legal age, and are the children sinful for this?

The retirement pension or social security is a matter of disagreement among scholars. Most of them permit it as long as the state manages it for the purpose of solidarity and not for profit. It is closer to cooperation and solidarity between the state and its citizens, and is not considered a financial exchange or a prohibited commercial insurance.

It is permissible to designate specific categories to benefit from it, such as females over males, or those unable to work, and to set specific conditions for benefiting, such as a certain age.

Therefore, there is no harm for the questioner and her sister to benefit from their parents' pension from this governmental social security, unlike their brother who has exceeded the legal age.