Like in most harvest moon games, your character has to get married to a villager at some point and in this game, its no different. I will edit who else is available as I learn more. But so far, this is who I know is single and looking.

Cryil - Fisherman
Gabriel - Livestock owner's son
Edmond - Head Mage (he may look old, but that's just his magic)
Gareth - Apprenticing wizard
Dean - florist's son

Melanie - Blacksmith's grand-daughter
Jeanne - doctor
Tabitha - world's number one witch
Nova - Gorgan's daughter
Harvest Goddess