Is it permissible to give charity from money previously acquired through unlawful means—while unaware of its unlawfulness at the time—to a relative who is about to get married, especially since this relative requested a loan and the giver has no money to lend him?

It has been previously stated that any illicit money remaining in the possession of the inquirer should be spent on charitable causes and not be personally benefited from, with the allowance for a penitent person to benefit from a portion of it if they are in need. Among the charitable causes is assisting someone who wishes to marry, in order to achieve chastity and protection. Thus, there is no harm in giving this money or a part of it to a relative who is about to marry. This is not considered charity (sadaqah (definition)) or zakat (definition), but rather a disposal of illicit money, because charity and zakat can only come from lawful wealth.