Read Way To Heaven Manga:
A strange relationship began when orphan siblings met an old lady who claims to be their grandmother. However, the old woman is a Grandmaster from Murim, who has lost her memory loss due to a disease.
The old lady recognizes the hidden talent of the eldest sibling and starts to train him. Thus begins the journey of last disciple of Jinmu Shin Mo, the boy who is destined to reach the pinnacle of heavens.