Grandma Mi has died of a deadly heart stroke! She had survived a long time and had been living single for decades. Before dying, she finally told Tarzan and the whole main cast that she adopted Tublat because his birth parents simply weren't fit for him, so she became a mother figure to him.
Tarzan then had to bury her in flowers and mud. Just as Terkoz came in with his own adopted son Goyat!