Watch Brody Jenner Smack a Man For Touching Kendall Jenner's Butt

Brody Jenner's got his sister's back.

In this clip from Sunday's all-new Keeping Up With the Kardashians, Brody, 30, defends his half-sister Kendall Jenner, 18, when a man gropes her at a bar during the family's vacation in Thailand.

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After the man is seen touching Kendall, the model quickly moves away from him, with a shocked "Excuse me!" before quickly informing Brody of the situation.

Not surprisingly, the former Hills star was having none of it.

"Did you just f**king touch my sister?" he confronts him.

… And things quickly escalate from there when Brody smacks the sunglasses off his head.

Watch the video to see the tense confrontation go down.

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Keeping Up With the Kardashians airs Sunday, August 3 on E!