In Bereshit 12:3 HaShem tells Avram:
וַאֲבָֽרְכָה֙ מְבָ֣רְכֶ֔יךָ וּמְקַלֶּלְךָ֖ אָאֹ֑ר וְנִבְרְכ֣וּ בְךָ֔ כֹּ֖ל מִשְׁפְּחֹ֥ת הָֽאֲדָמָֽה׃
And I will bless them that bless thee, and him that curseth thee will I curse; and in thee shall all the families of the earth be blessed.
While in Bereshit 18:18 it says:
וְאַ֨בְרָהָ֔ם הָי֧וֹ יִֽהְיֶ֛ה לְג֥וֹי גָּד֖וֹל וְעָצ֑וּם וְנִ֨בְרְכוּ־ב֔וֹ כֹּ֖ל גּוֹיֵ֥י הָאָֽרֶץ׃
seeing that Abraham shall surely become a great and mighty nation, and all the nations of the earth shall be blessed in him.
At first sight I thought they meant the same thing, but then the differences between these two verses stood out: One talks about Mishpechot, while the other talks about Goyey, one talks about Ha'Adamah while the other talks about Ha'Aretz.
Whats the difference for, what does it imply and what is the nuance between these two verses. For they don't seem to refer to the same thing.