Which of the following contains a vague pronoun reference?

 - Ron's brother wasn't feeling well, so Ron had to stay home with him.
 - Ron had to stay home with his brother because he wasn't feeling well.
The first answer choice contains a vague pronoun reference. The pronoun he could refer to Ron or his brother.
Ron had to stay home with his brother because he wasn't feeling well.
The second answer choice shows a possible correction for the vague pronoun reference. The text has been rewritten so that the meaning is clear.
Ron's brother wasn't feeling well, so Ron had to stay home with him.