Jean Baptise Charbonneau (nickname Pompy which was given to him by William Clark) was the first child of Sacagawea, a 16 year old Shoshoni girl who had been captured from her people years earlier by a tribe of natives called the Minnetarees.

To obtain her services Lewis and Clark hired her husband Toussaint Charbonneau as interpreter. Lewis and Clark also allowed Sacajawea to bring her child Jean Baptiste Charbonneau.

William Clark made a promise to Toussaint and Sacajawea to send young Jean to school. In 1810 Charbonneau and Sacajawea brought Jean Baptiste to William Clark who took charge of the youngster and put him in school.

In 1824 Jean Baptiste met visiting German Prince Paul of Wurttenberg and traveled with him in Europe. Eventually he became an interpreter and guide among the Indians; one of the white men he later guided was Clark's own son Jefferson.

He died in Oregon in 1885 at the age of 80. There is a popular belief Sacajawea lived to the age of 100 and died in Wind River country of central Wyoming, more substantial evidence points to a much earlier death.

Toussaint lived to old age, eventually vanishing from the prairies of Upper Missouri, where he served as Government interpreter among the Mandans.

(a lot of this information came from the National Geographic Book "In the Footsteps of Lewis and Clark" by Gerald Snyder.)

As for Mary Brown who was 1/4 Indian if I was to take a guess I believe that it is very likely that she was the daughter of Jean Baptiste. Also trying checking with the Western Shoshoni Indians of Wyoming.

If I can find more information I will post it.