Ryker decided to not talk of his parents for now. While it might be questionable for those from outside, him, who spend most of his life with them could tell there is a deeper reason for their action.
Though, he doubt they would truly understand, so it's better to continue the talk of Source Grand Realm.
"When you manage to create the Earth Source as it is called, you will be considered to reach the True Earth Realm. After that, you can ascend to the Heaven Realm.
The Heaven Realm is split into Lower Heaven, Upper Heaven, and True Heaven. You will only be consider to reach the Heaven Realm when you step into the Lower Heaven Realm.
To do that, you will need to create the Lower Heaven. Heaven is associated with sky, so, Lower Heaven meant the lower level of the sky.
For instance, clouds, and air current is what encompassed what is considered the Lower Heaven in the Heaven Source Realm.