My father, who refuses to ask for directions, drove us straight into a swamp. Luckily, the brother who brought his GPS was in the car with us. Our rental van, which was already making weird noises, finally broke down completely.

Why the punctuation matters:

• You only have one father, so "My father" is already a uniquely identified person. The clause gives extra, humorous information, so it gets commas (non-defining).

• The phrase "the brother" implies there is more than one brother, so the clause "who brought his GPS" is essential to identify which brother we mean. No commas are used (defining).

• "Our rental van" refers to a specific, single vehicle they are using. The weird noises are extra info, so it requires commas and "which".