Conversation so far:
What about William Henry Dietz heritage was contested?
Dietz's heritage was first contested in 1916 after former neighbors who settled on the Pacific Coast heard he was posing as an Indian.
Was William Henry Dietz living on an Indian reservation or had he lived on one before?
It is not confirmed whether William Henry Dietz actually was born on the Pine Ridge reservation in South Dakota or not.
Who was William Henry Dietz impersonating when the FBI investigated him?
The Bureau found William Henry Dietz had taken on the identity of James One Star.
Did William Henry Dietz do any jail time for the identity fraud?
William Henry Dietz ended up with a 30 day sentence in the Spokane County Jail after he pleaded no contest.

Question: Did he have any other Indian brothers and sisters from the mother that testifed for him?
Self-contained rewrite: Did William Henry Dietz have any other Indian brothers and sisters from the mother that testified for him?