Albert Barnes Commentary 2 Kings 10:1

"Now Ahab had seventy sons in Samaria. And Jehu wrote letters, and sent to Samaria, unto the rulers of Jezreel, even the elders, and unto them that brought up [the sons of] Ahab, saying," — 2 Kings 10:1 (ASV)

Seventy sons - that is, descendants; this number included the children of Jehoram (2 Kings 10:2–3 and following).