In Haida, possessors that form a constituent with the possessed noun (determined based on word order, for example) can control number agreement on the verb such that the verb indexes the number of the possessor, and not that of the possessed noun. This type of agreement is also found with arguments, i.e. the same plural marker that indicates the number of a subject or an object indicates the number of a possessor.
See also Aleut.
Enrico, John. 2003. Haida syntax. Lincoln: University of Nebraska Press.
Leer, Jeff. 1991. Evidence for a Northern Northwest Coast Language Area, International Journal of American Linguistics 57(2): 158-193.