The following are interesting documents relating to the Kelseys

There are two recent (March, April 2022) articles on the proposed renaming of Kelsyville:

They were some of California's most brutal slave owners.

Their deaths sparked a massacre - San Francisco Chronicle.

Various Names Given to Kelseyville - By Kevin Engle

An Act of Survival - By Kevin Engle

The Kelsey Brothers: A California Disaster - By John Parker
Talk presented at the 2012 November meeting of the Lake County Historical Society

Dr Parker gave a similar talk on the Kelsey Brothers at the Ely Stage Stop Museum, on Saturday October 9th, 2021. This was videotaped by Euston Productions, and can be viewed here :

The ACLU (Northern California) has a series on "Gold Chains - The hidden history of slavery in California". Of particular interest are:

Bloody Island Massacre As many as 200 Pomo were killed on the island and in the surrounding area. Many women and children were stabbed with bayonets. One of the few survivors was a 6-year-old girl named Ni’ka, later known as Lucy Moore, who hid in the bloodied waters and survived by breathing air through a reed. The seeds of this bloody conflict can be traced back to 1847 when two white settlers, Charles Stone and Andrew Kelsey, bought a cattle ranch where they kept several hundred local Pomo men as slave laborers. 

Rosa: Kidnapped, Sold, and Killed Rosa was between 10 and 12 years old and was believed to be from either the Yuki or Pomo tribe. In the winter of 1862, she was beaten and left to die in a snowstorm by a woman who had been granted legal custody of her under the law. 

A History of Napa and Lake Counties - By Lyman L. Palmer 1881 This is rather old, but does represent a contemporary view.