In Bac Home Loans Servicing, L.P. v. Savankham, 2016 Mass. LCR LEXIS 86 (Mass. Land Ct. 2016), a mother gave a bank a mortgage on her joint tenancy interest in property she shared with her two children. The children did not know about or participate in the transaction. Apparently, the bank thought it was getting a mortgage on the whole property rather than just the joint tenancy interest of one joint tenant and sought to reform the documents to reflect that understanding. However, because there was no proof that all parties understood the transaction this way, it was a unilateral mistake of the bank rather than a mutual mistake of all owners and the lender. The court refused to reform the documents to reflect the arrangement the bank wanted or thought it was getting. A word to the wise, I suppose. You really need to do a title search to make sure the one granting the property interest actually owns it. One might have thought the subprime crisis problems that brought such issues to light would cause banks to be more careful but mistakes apparently still can be made.