Unfinished Tales
According to an alternate account about the line of the Princes of Dol Amroth cited in "Unfinished Tales", they were descendants of a family of the Faithful from Númenor who had ruled over the land of Belfalas since the Second Age, before Númenor was destroyed. This family of Númenóreans were akin to the Lords of Andúnië, and thus related to Elendil and descended from the House of Elros. After the Downfall of Númenor, they were created the "Prince of Belfalas" by Elendil "Unfinished Tales" provides an account of "Adrahil of Dol Amroth" who fought under King Ondoher of Gondor against the Wainriders, which predates Amroth's drowning in TA 1981.