爸 is not an ancient picture of a father. It is a sound-and-meaning character: 父, “father”, supplies the meaning, while 巴 supplied a sound clue. The character entered the written tradition as a spoken word for father, so this component sketch shows 父 above 巴 instead of inventing an oracle-bone ancestor that is not securely attested.
A piece of culture
A family word across languages 爸爸 is the warm everyday word “dad”. In Mandarin it is usually bàba, with a light second syllable; in Cantonese it is baa4 baa1. Similar “ba” sounds for fathers occur in many unrelated languages, but that resemblance alone does not prove that the words share one origin. Here, 爸 also makes a useful family bridge to 父, the older and more formal character for “father”.