Am I sinful for taking out an interest-bearing loan to help my brother and pay off my debts, knowing that I did so under pressure and insistence from my parents?

Borrowing with interest (riba) is one of the major sins forbidden by the Qur'an, Sunnah, and scholarly consensus. No one is permitted to command it or be obeyed in it, even if it is one's parents, because the Prophet (peace be upon him) said: "Obedience is only in what is good and permissible." In this situation, there is no necessity to engage in usurious transactions due to the existence of permissible alternatives and the possibility of postponing marriage. The borrower, his father, and his brother must repent to Allah by feeling remorse and resolving not to return to it, and hasten to repay the remaining borrowed amount to sever the usurious transaction and be rid of the interest.