Why father’s first letter is capital [duplicate]
After they had their supper, Father went into the living-room to watch TV.
Why use Father not father?
"Father", in this case, is being used as a proper noun. For this reason, it being capitalized is correct.
If the author had written "my father" or "the father", "father" would not be capitalized as it wouldn't be a proper noun in those cases, it would be a common noun.