What is the meaning of "Imru la'Acheichem Ami"?
Radak citing Rav Sadya Gaon: Tell Shevet Yehudah and Binyamin, your brothers, the 10 tribes, who were called Lo Ami when they did evil in Hashem's eyes, when the exiles return, they will be called Ami.
Why does it say "vela'Achoseichem Ruchamah"?
Radak: The Mashal was with a son and daughter ? therefore it says Acheichem and Achoseichem. There is only one plural in Achoseichem (your (plural) sister) ? if there were two plurals (your sisters), it would say Achiyoseichem, just like "v'Es Achai v'Es Achiyosai" (Yehoshua 2:13).
What should they say to their siblings?
Rashi citing Targum Yonasan: Return to My Torah, and I will have mercy on your assembly.
Malbim: Since the number of Bnei Yisrael will be like the sand, I command the sons and daughter to tell their brothers [whom they wanted to call Lo Ami, that they are Ami] and your sister [whom they wanted to call Lo Ruchamah], that she is Ruchamah. In the future they will be Am Hashem, and Hashem will have mercy on them. Here he claimed against Hashem 1 , who wanted him to expel his wife and call his sons Lo Ruchamah and Lo Ami.
Even though the verses imply that one party said verses 1-15, and it concludes "Ne'um Hashem", Malbim holds that Hoshe'a said verses 1-3 ? a Brachah amidst Hashem's rebuke. However, it is not clear to me whom Hoshe'a addresses in this verse. (PF)