The 1892 RLDS edition accidentally replaced the pronoun us with them, probably because the preceding clause uses the pronoun they. The 1908 RLDS edition reverted to the correct us. The original text here intends to say that the descendants of Lehi are among those who are broken off and that they will be remembered because all those who have been broken off will be remembered. The incorrect use of them simply ends up creating an impossible redundancy (with the meaning ‘the Lord remembers all those who have been broken off; therefore he also remembers all of them’).
Summary: Maintain the original pronoun us in 2 Nephi 10:22; the accidental replacement of us with them in the 1892 RLDS edition created a difficult reading.