I have added the following NPC’s from the Dragonborn DLC to the list. As far as I am aware none of the NPC’s from the Dawnguard DLC are available for Marriage.
Females
Hillund – Nord – Warrior – Bujold’s Retreat / Thirsk Mead Hall - Complete Retaking Thirsk and collect 50 Riekling Spears for her.
Morwen – Nord – Skaal – Skaal Village - Freeing the Skaal, After delivering her mothers amulet to Runil in Falkreath.
Males
Halbarn Iron-Fur – Nord – Blacksmith - Bujold’s Retreat / Thirsk Mead Hall - Complete Retaking Thirsk and Halbarn's Supplies.