This has nothing to do with understanding, but everything to do with grammar rules.
READ THE FOLLOWING FROM http://www.chompchomp.com/terms/pronounreference.htm
A possessive noun should not be the antecedent for a pronoun.
Possessive nouns function as adjectives. You can drive a fast car, a red car, a dirty car, or Mom's car. Fast, red, and dirty are all adjectives telling us which car. The possessive noun Mom's is adjectival too.
You ruin the clarity of a sentence when the antecedent for a subject or object pronoun like he or him is a possessive noun.
Read this example:
Kevin's fingers were strumming the guitar when he winked at Donna.
When we read this sentence, we assume that Kevin is the he winking at Donna. But remember that Kevin's is adjectival, not a noun. If we replaced Kevin's with agile, quick, or long, we wouldn't consider any of those adjectives the antecedent for he, so we shouldn't consider Kevin's either. And the fingers certainly aren't doing the winking as they have no eyes!
Furthermore, a reader might wonder if the whole Kevin is strumming the guitar or if just his disembodied fingers are making the music. The sentence in its current version is unclear.
To fix the problem, you can replace the pronoun with a specific noun. You can't have a pronoun reference error if you have no pronoun!
Kevin's fingers were strumming the guitar when this young man winked at Donna.
Or you can revise the sentence so that the pronoun refers to a real noun—that is, a real antecedent:
As Kevin strummed the guitar, he winked at Donna.