Complex sentence: He belonged to a large and influential family within the Absentee Shawnee Nation where he was an active member of the community and became a Peyote leader when the Native American Church was first adopted by Shawnee people.
Split into simpler sentences: He belonged to a large and influential family within the Absentee Shawnee Nation. He was an active member of the community and became a Peyote leader when the Native American Church was first adopted by Shawnee people.