Husbands Secret Debt

[missysup]

I found out about 6 months ago my husband got a loan for his sister to go to Argentina to get surgery(Cosmetic). I did not sign any paperwork and my name is not on this debt however I am married to him. Dearest sister has missed a lot of payments and has got caught back up. If she don't pay this bill can the debt come after my things or just joint accounts? I am worried that his bad decision will effect the well being of me and my children.