Do you have any first names for the Willis' that you are looking for? There are many Willis' names, some shown as Chickasaw, some as Choctaw, even though they come from the same family originally. Its probable these brothers (white)were married to women of both the Chickasaw and Choctaw Nations....which would account for the tribal differences in these lists among their descendents.
Britton Willis, a white man ( born 1758, died 1844) was a Revolutionary War veteran from South Carolina. He was the father of:
James Willis married Amanda Love and had at least 2 children:
James Hampton Willis
Reuben B. Willis
When Amanda died James married her sister Elvira.
Both of the sons married women of Indian descent. Both moved from Mississippi, and came to Indian Territory.
1 James Hampton Willis
2 Reuben B. Willis.
Both of these sons were listed as white men living among the Chickasaw. Both married Indian women. Descendents married into both the Choctaw and Chickasaw Nations.
If you think that either of these may connect to your Willis lines, please let me know and I will give you what I have on these families. You can contact me direct at: firstname.lastname@example.org