It depends.
First of all, it depends on the name of the house and car that your husband is going to pay off his debts, and whether it is the joint property of the husband and wife within the marriage.
First, if it is not the common property of marriage, and the house and car are in the name of your husband or in-laws, then you can only dissuade this matter and have no right to stop it. Because this is pre-marital property, you have no right to dispose of it. And it may be the property purchased by in-laws, so when their son needs to repay gambling debts, it is completely justified for others to call their own property. Or your husband's personal efforts before marriage, he has every right to deal with it. You can't stop it.
Second, if you and your husband's domestic common property, joint investment, joint loan, or as long as they are purchased during the marriage, they are all yours. You have half the right to dispose of the house and car, and your husband has no right to pay off his brother's debts. You have the right to stop it. If you can't stop it, you can use legal weapons to safeguard your legitimate rights and interests.
Besides, aside from the above, I think it is problematic for your husband to "take" the house and car to pay off his brother's debts instead of "borrowing". Unless you are a multimillionaire, who can give away your house and car for free? Besides, your husband's brother is still a "usurer", isn't he rich compared with his property?
I think, regardless of the ownership of the property, you should convince your husband that even if you really want to help pay off the debt, you should "borrow" it and have formal IOUs, loan vouchers and notarial certificates. The law is guaranteed. After all, no one's money is blown by the wind. If your husband's brother is addicted to gambling or something, it's a bottomless pit. You can't put your family in there for him. So there must be an iou. Can only borrow, can only return.