Chief Mad Bear is Lower Yanktonais and recorded on all the census as Lower Yanktonais. His wife was Santee. His family is as follows:

In the 1889 Standing Rock Census
Mad Bear- 51 years old
First Woman-51 years old
Cow Walking Woman-23 years old
Helper-18 years old
Pretty Girl-15 years old
Handsome-11 years old
No Help-8 years old
Catherine Mad Bear-4 years old
— LaDonna Brave Bull Allard

Donovin Sprague has some information about him: “Mad Bear was born in Minnesota near the Mississippi in 1836. (…) Mad Bear´s father was Loud Thunder and his mother was Black Lightning Woman. His brothers include Elk, Crazy Bear, Walks In The Wind [ ! ], Bobtail Bear, Crow Feather and Black Cloud. His sister was Refina Mad Bear.” (See Donovin Sprague, Standing Rock Sioux, Arcadia Publishing, page 11) — Dietmar Schulte-Möhring

1889 Standing Rock census, I found:

Mad Bear-Lower Yanktonais age 51

Bear Paw -Lower Yanktonais age 25

Mad Bear 2-Lower Yanktonaid age 30

Walks in the Wind-Lower Yanktonais age 28

Bobtail Tiger-Lower Yanktonais age 33

— LaDonna Brave Bull Allard