“It's very dry.”
Your brother tells jokes without laughing, so you can never tell whether he's joking. You're talking about him with your daughter, and she says, "He has a weird sense of humor." You agree, and add this to describe his sense of humor more specifically.
It's very dry.
A person with a "dry" sense of humor often says funny things with a serious, calm expression. They don't smile, laugh, or make silly faces. Here's an example in a sentence:
She has a dry sense of humor.
Some people really like a dry sense of humor; other people don't understand it very well. it can be either positive or negative to say that someone has a "dry" sense of humor.