Can my deceased father's common law wife claim his social security benefits? She is a Canadian citizen.
I can't answer that question without much more information. Canadian citizens can be eligible for widow's benefits from Social Security, but they must meet all of the requirements for entitlement (https://www.ssa.gov/OP_Home/handbook/handbook.04/handbook-0401.html).
Furthermore, in the case of a common law marriage, Social Security must establish that the marriage was legal under state law if it occurred in the U.S. (https://secure.ssa.gov/apps10/poms.nsf/lnx/0200305075), or in the applicable province if it occurred in Canada (https://secure.ssa.gov/apps10/poms.nsf/lnx/0200307255).