Was Jeroboam from the royal family line?
No, Jeroboam was not from the royal family line. When the ten northern tribes seceded after Rehoboam refused to lower taxes, they appointed their own king, Jeroboam, who was not in the kingly or royal family line. Rehoboam, Solomon's son, continued on his father's throne in Jerusalem.
Les explains that after Rehoboam refused to lower taxes and keep peace, the ten tribes of the north seceded and said they would have their own king. That king was Jeroboam, and Les points out he was not even a man from the kingly or royal family line. Meanwhile Rehoboam, Solomon's son, set up his throne in Jerusalem, where the temple was, over Judah and Benjamin, while Jeroboam became king of the northern ten tribes.