Is the sale by a couple of a house owned by the husband to pay off a usurious loan that they both owe, and giving part of the sale price to the husband’s unemployed brother who lives with them in it, considered an injustice to this brother? And is the husband’s ownership of this house in this manner in accordance with Sharia?

It appears that the questioner's father-in-law registered the house in his son's name and continued to live in it with his wife and some of his children until his death. This does not constitute a valid hiba (gift) due to the lack of legal possession ( عدم الحيازة الشرعية). Therefore, the house is a joint property to be distributed among all heirs. As for the usurious loan, accelerating its repayment is desirable if it eliminates the interest; otherwise, there is no benefit in rushing it. The borrower must make sincere repentance and not return to such loans. Purchasing a car is not a necessity that permits usurious borrowing.