All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
No doubt taking interest-based loans whether they are for purchasing a house or for anything else is forbidden. Know that dealing with Riba is among the major sins. May Allah Protect us from all kind of sins.
Therefore, the one who was involved in such a sin should sincerely repent to Allah and ask His forgiveness. You are not obliged to sell the house since the house is not Riba (usury/interest) but the Riba is the sum you pay to the bank more than what you have received. Thus, the borrowing person is sinful due to his cooperation in dealing with Riba. Jaabir, may Allah be pleased with him, narrated that the Prophet said βAllah has cursed the one who consumes Riba (i.e. usury or interest), the one who gives it to others, the one who records it and the one who witnesses it (its transaction).β He added: βAll of them are equal in sin.β [Muslim]
Allah knows best.