This is how you sign Brother in law in American Sign Language.

How to sign

To sign "Brother-in-law" in American Sign Language (ASL), follow these steps: 1. Make both hands into an 'L' shape with your thumbs and index fingers extended. Hold your non-dominant 'L' hand down by your chest. Take your dominant hand and starting at the forehead, forming the tip of a baseball hat, bring the hand down to rest on your non-dominant hand, transforming it into an 'L'. 2. Touch the palm of your right "L" hand to the left palm, then pull it off slightly, move it down, and touch the left palm again.