Catherine's brother James & Isabella's brother John arrive in Bath together. And they immediately meet up with Catherine & Isabella (what a lucky coincidence!).

It is clear that James Morland is smitten w/ Isabella, and that she encourages him. James greets Catherine warmly, however, and appears to fit the Morland mold quite well. John Thorpe greets his sister carelessly, but that's not bad in itself. The reader's initial impression of Thorpe is (probably) similar to Catherine's impression: he's trying hard to impress, unsuccessfully, and he ends up demonstrating how crude & vulgar he is.

Thorpe talks too much, says too little worth hearing, and is contradictory throughout. I didn't mind the way he talked to his mother & sisters, even though it's very crude & rude & disrespectful, having known families where people talk that way even though they are very affectionate. But he's a braggart, and Catherine is right to be suspicious of his character.