Final answer:
To reduce ambiguity in the sentence about two brothers, 'he' is the correct pronoun choice since it is clear that the sentence refers to a male sibling.
Step-by-step explanation:
To reduce ambiguity in the sentence 'Of the two brothers, ______ is more conservative.' the correct pronoun to use would be 'he', since brothers refers to male siblings. Using 'he' clarifies that the sentence is talking about one of the two males previously mentioned. The other pronoun options would not make sense in this context since 'she' refers to a female, 'they' could imply both brothers or a non-binary person, and 'we' implies the speaker including themselves in the comparison.