A Time-Travel Masterpiece: the Protagonist Will Be My Little Brother

This is an era full of dangers. There are ancient tribes, immortal tribes, and all kinds of races. However, the same thing is that no one can enter the legendary fourth step. For thousands of years, only a handful of people have entered the Sky. And I, at the beginning of the time travel, accepted the future Sky-Treading strongman as my younger brother. At this time, he was only a child. What should I do? This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.