Is this sentence a dangling participle or a missing modifier?

My father's grandfather and his brother fought at the battle of Vimy Ridge.

My first question looking at this sentence is, "Whose brother? Your Dad's, or his Grandpa's?"

There's some confusion over whose brother actually went to Vimy. How would you describe what's wrong with the above sentence?

Solution 1:

First of all, there is no ‘participle’ and so no dangling participle. Nor is there a dangling preposition (which is the commonly recognised dangler).

If there is a problem, it is in the potentially ambiguous reference of “his”: it could refer to the brother of the father of the subject of the sentence or to the brother of the subject’s father.

It is a common problem with pronouns and with possessive adjectives. Common sense suggests that it is probably the grandfather’s brother (i.e. the the father’s great uncle that fought at Vimy Ridge. It stretches credulity that someone’s uncle and great great uncle both fought in the same battle.

Ambiguity is not a grammatical fault. But if it is to be avoided, it is by finding another way round it. For example:

My great grandfather and his brother ....

This will do fine.

Solution 2:

This is called an unclear antecedent or ambiguous antecedent. The default rule when parsing an ambiguous antecedent is to assume it refers to the most recent sensible noun. So in your example, we'd assume it's Grandpa's brother.

One way to fix it would be to avoid having two possible antecedents in the first place:

My great-grandfather and his brother ...

In this version, it's clear that it's your grandfather's brother, because we never mention your father.

You can also avoid the pronoun:

My father's grandfather and brother ...

Now it's clearly Dad's brother.

You can find more discussion of this problem at The case of the ambiguous antecedent and Unclear Pronoun Antecedents.