GMAT Sentence Correction (SC) | According to recent studies comparing the nutritional value

Hi Expert,
can you help me by finding out my mistake in this regard?
I’m totally stuck with this sentence. The sentence is going to compare between meat from ‘wild animals’ and meat from ‘domesticated animals’.
B saysthat:
----------wild animals have less total fat than livestock fed on grain. -Correct. Compares the fat wild animals have to the fat that livestock (fed on grain) have.
If Isay: He is less successful than his father’s. -Father's is totally awkward here. Father's what? Here you must compare the success between 2 persons --> He is less successful than his father.