Legal Question in Wills and Trusts in Massachusetts

I'm sorry for your loss. You are right that MA doesn't recognize common law marriage. The answer to whether she would have an interest in the property depends on how the property was left to you and whether your brother left a Will. If your father left the property to the three brothers jointly with rights of survivorship, then you two surviving brothers own the property and your deceased brother's GF has no claim to ownership. However, if your father left the property to you as tenants in common, then your deceased brother's interest passes to his estate. If he had a Will, that document will determine who will take his interest. If he had no Will, then his interest would pass to his children equally. If the kids are minors, the GF, as their mother, can petition the Probate Court for guardianship and manage their interest in the property until they reach the age of majority. Good luck -