But when the time had fully come, God sent his Son, born of a woman, born under law, to redeem those under law, that we might receive the full rights of sons. Because you are sons, God sent the Spirit of his Son into our hearts, the Spirit who calls out, “Abba”, Father. So you are no longer a slave, but a son; and since you are a son, God has made you also an heir. See also John 1: 12 and 13
Not only are we no longer slaves, now we are sons (children) of God. We will receive the inheritance of sons. The difference here is, that the inheritance will not be divided up among the children, each getting a small portion. No, each of us who is a child of God will receive the full inheritance. Amazing!