お義父さん
Meanings
1
Polite term for one's spouse's father. Used both when addressing him directly and when referring to him in conversation.
I hear my father-in-law is retiring next month.
Father-in-law, would you like some tea?
2
Can refer to a foster father in a family context, though 養父 (ようふ) is more common for legal foster relationships.
He was raised by his foster father from a young age.
3
Used for a stepfather, especially in direct address or when speaking politely about him. 継父 (ままちち/けいふ) is a more formal or legal term.
I go fishing with my stepfather on weekends.