father-in-law
Schwiegervater is the German term for a father-in-law, the father of one's spouse. This term is used to refer to the father of either a husband or a wife. It is a compound word made up of 'Schwieger', which is a prefix used to denote in-laws, and 'Vater', which means father.
My father-in-law is a teacher.
This sentence is a simple declarative statement which is sharing an information about the profession of the speaker's father-in-law who is a teacher.
I am going shopping with my father-in-law.
This sentence signifies an ongoing or planned action. Here, the speaker is indicating that he or she is planning to, or is already, going shopping with their father-in-law.
My sister's father-in-law is nice.
This sentence is expressing an opinion about the father-in-law of the speaker's sister. The speaker thinks that the personality of their sister's father-in-law is nice.