Well, let's see here... I plan on having a total of 12 Shepards when all is said and done, and a few of them will probably wind up being single.
Rowena, the paragade soldier, is 100% Garrus.
Dick, the renegon vanguard, went for both Ash and Miranda.
Joanna, paragade infiltrator, stayed faithful to Liara.
Jasmine, the renegade adept formerly known as HotWings, almost romanced Kaidan, but he died. She might go for Jacob. Scratch that--she'll definitely go for Jacob.
Next up is Bradley, the renegon engineer, and I'm not sure what's up with him. Ash? Liara? Tali? Dunno, man.
Zeke the paragon sentinel might be gay, but he might go for Tali if Brad doesn't.
Braxton, the renegade soldier, might go for Ash.
Anabelle, paragade vanguard, will be with Kaidan and might accidentally Garrus.
Malcom, the paragade infiltrator, will definitely be romancing Jack.
Freddie, the paragon adept, is gay, so he'll be waiting for Kaidan.
Alexandria, engineer and Sith Lord, will either romance everyone or romance no one.
Finally, Madison, the renegon sentinel, might hook up with Kaidan but will definitely be a Thane girl.
So at least one is single for sure.