To do the sign for "uncle" hold a "U" hand to the side of your head. Twist
it twice. The sign Uncle is done higher up than the sign "Aunt."
UNCLE:




Uncle: (variation)
Some people shake a "U" handshape side to side using a very small repeated
movement. Again, the position is to the side of your head, a bit higher up.
(Near your ear or higher, rather than near your cheek or lower.)

See:
AUNT
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American Sign Language (ASL) online at American Sign Language University ™
ASL resources by Lifeprint.com © Dr. William Vicars