In order to be written in the book of God's Family, we need to be registered. In the bible it is mentioned about a Book of Life. Registration is entering the Book of Life. All those who are Blessed are children of God. Blessed families before the Registration Blessing ceremony are like illegitimate children of God.
Illegitimate children have no rights to inherit things from parents.
To receive the Registration means to become legitimate children of God. After Father gave us the Registration Blessing he said he now has a different attitude to us, as now we are entered into the direct lineage of God. He said that before we received registration, our mistakes could be forgiven, but after registration in the book of God's Family, it will be impossible to forgive us. Therefore we have to be very strict in our lives to keep God's word. Father also said that in the spirit world, Heung Jin Nim, Young Jin Nim, Dae Mo Nim and others, have received special orders from True Parents to look over the Registered Families.