1. She married [ a ] son of the Louis Vuitton owner.
2. She married [ the ] son of the Louis Vuitton owner.

I think both are correct. When there is [a], it means, the speaker focuses on the fact that the speaker doesn't have any clue about the son. He could be the 1st one or the 2nd one or something else. When there is [the], it sounds like emphasizing Louis Vuitton. He is not a son of someone in a common family.

Am I wrong?

And is it incorrect to put [the] before Louis Vuitton owner?

Thank you!

Question

1. She married [ a ] son of the Louis Vuitton owner.
2. She married [ the ] son of the Louis Vuitton owner.

I think both are correct. When there is [a], it means, the speaker focuses on the fact that the speaker doesn't have any clue about the son. He could be the 1st one or the 2nd one or something else. When there is [the], it sounds like emphasizing Louis Vuitton. He is not a son of someone in a common family.

Am I wrong?

And is it incorrect to put [the] before Louis Vuitton owner?

Thank you!

Answer

“A” and “the” can be used interchangeably. “The” CAN indicate that there is only one son, but it might not. Even if there are five sons you can still say “she married the son of the owner”. The reason that works is that “the” goes with “son”. She married someone’s son. How many sons the father has is irrelevant. Whether to say “a” or “the” depends on context.

Answer

The first statement indicates that the Louis Vuitton owner has more than one son and the speaker is not making it clear which of the sons was married. The second statement is the opposite: the speaker is referring to a specific son, but it is not clear if the Louis Vuitton owner has additional sons.

Yes, it is correct to put “the” before Louis Vuitton owner.