Here's why:
* Pronoun Case: "He" is the nominative case, used for the subject of a verb. "Him" is the objective case, used for the object of a verb or preposition.
* Parallel Structure: When listing multiple people, you should use the same case for each pronoun. Since "his father" is in the nominative case, "he" should be used as well.
Example:
"His father and he went to the store together."