Hi and thanks for your question.
If he transferred his interest in the house to his sister-in-law by deed, then that deed should be recorded with the registry of deeds in the county where the property is located. This is a public record, so you can search the registry to determine whether this occurred. If he properly transferred all of the ownership interest in the house to his sis-in-law, then you would not have a legal right to it. This is all assuming that he has the legal right to transfer all of the ownership interest in the house to another.
I hope that this answers your question (even if it's not necessarily the answer you wanted to hear); if so, please click the green Accept button. Thanks very much and I wish you well.
Attorney
More than 11 years experience with estate document preparation, litigation and mediation