Let's look at all the answer
I know that Tenskwatawa was a Shawnee
Sitting Bull was a Hunkpapa Lakota Leader so it wouldn´t be him
Tecumseh was a Shawnee Cheif who planned a Native American confederacy to stop white settlement in the Northwest Territory
Sacagawea is a native American explorer but she would not be a brother since she is a girl so its not her
If its a multiple-choice answer I would choose Tenskwatawa and Tecumseh
Although Tenskwatawa is Shawnee I don´t see info of him helping to form a coalition of Native Americans to defeat settlers taking their land
My final answer would be Tecumseh