What is the ruling on eating from the money of relatives earned through usury, and how can one maintain kinship ties with them?

There is no objection to eating the food of relatives who have taken out interest-bearing loans, or who have guaranteed an interest-bearing borrower, or to accepting their gifts, or sitting in their house which they bought with an interest-bearing loan; because the interest-bearing loan is tied to their liability, not to the money itself.

It is obligatory to deal with these relatives kindly, while gently advising them to abandon this major sin.