father-in-law; stepfather; foster father
Refers to a father by legal or social tie rather than blood: a spouse's father, a stepfather, or a foster father. The exact relationship is usually clear from context.
My father-in-law is a very kind person.
He lives with his stepfather.
義理 (duty, obligation, or in-law relationship) + の (possessive particle) + 父 (father). The phrase literally means 'father of obligation/affinity', referring to a father by social or legal bond.