What's the meaning “them” here?

Question

I've confused about the word "them" in the middle of the sentence:

They know all about them Westovers in Idaho.

Could you please tell me what the meaning of "them" here is?

Does it mean "they know about the oils which are made by Westovers in Idaho"?

The full text is here:

Dad had always said he wanted to build a room the size of a cruise ship but I’d never thought he’d have the money. I looked to Mother for an explanation but it was Dad who answered. The business was a roaring success, he explained. Essential oils were popular, and Mother had the best on the market. “Our oils are so good,” he said, “we’ve started eating into the profits of the large corporate producers. They know all about them Westovers in Idaho.”

Educated by Tara Westover

Answer 1

As has been mentioned in the comments, the word 'them' is a colloquial substitute for 'those'.

I would say you're partially correct in your understanding of the sentence. Taken at face value it does mean that the large corporate producers know about the Westovers in Idaho, who produce oils. However, I don't think he's saying this because he knows that the corporate producers know who the Westovers are. What he's really saying is that he's proud to have had an effect on the corporate producers' business. He's boasting about challenging the bigger producers for market share.