There is no indication in Tolkien’s writing that the Kings of Gondor were ever categorised into ‘lines’, as the Kings of Rohan were. I am aware of some secondary material that does so, and while it isn’t outrightly incorrect, I would point out that the Kingship of Rohan jumped from one line to the other in the female line, whereas all jumps in the Kingship of Gondor were to male sidelines. So I would like to avoid any impression that the use of term for the Gondorian royal house is authentic.
Moreover, if one does count ‘lines’ of the Kings of Gondor, the second line started with Eärnil I, the third with Calmacil and the fourth with Tarondor, so Eärnur belonged to the fifth ‘line’, not the third. I’m therefore correcting the number and putting the term in quotes. — Mithrennaith 00:25, 8 September 2010 (UTC)