“brothers.” In this context, “brothers” can mean, and probably does mean, relatives, not actual brothers.
“pay our respects.” The Hebrew is an idiom, literally, “seek the peace.” In this context it means to pay one’s respects or in that context, to visit with. These men were relatives of Ahaziah king of Judah, but because of the close ties between Judah and Israel at this time they were going north to visit the relatives of King Joram of Israel and Jezebel, the queen mother.
“queen mother.” The Hebrew word translated “queen mother” is gebereth (#01404 גְּבֶרֶת), and in this context the “queen mother” is the mother of the king (BDB Hebrew and English lexicon). The queen mother was the most powerful woman in the kingdom, much more powerful than any of the wives of the king, who often did not have much real power at all. That relatives of King Ahaziah, king of Judah, were going to see Jezebel the queen mother shows how much power and influence Jezebel had in the kingdom of Israel.