Treebeard is the oldest ente. Ente is a "shepherd of hundreds of trees", which is similar to trees in appearance. At the end of the third era, due to the large number of trees in the van Gung forest being cut down by Saruman, Shuxu led ente to attack the fortress eisengard of Saruman.
Treebeard is one of the oldest people in the land of Central Asia. During the twin tree era, before the stars were lit, jafana, one of Vera, created the ente race. Treebeard's lover is ente's mother, fimbrisher, but like all other entes, fimbrisher left ente's garden and disappeared after the war between the Numenor and Thrawn.
Source: @thatgirlthattattoos