Is your single, Dull, Messy or too Shy? They needn't be any more! First of all play the game and save it, then quit the game. Open the 'savegameXInfo.dat' file in notepad (X is the saved game you want to edit e.g. savegame3Info.dat)
You can find the file in the 'savegame' folder where the singles game is located. Now search for 'characterConditionValues', when you find it change the values

The values run from 0 to 9

Stat type Stat=Value
(introverted-extrovert) 0 = 9
(down to earth-playful) 1 = 9
(Messy-tidy) 2 = 9
(unfriendly-frendly) 3 = 9
(stable-neurotic) 4 = 9
(unknown) 5 = 4
(unknown) 6 = 6

Because you have two singles do another search and edit the values again. Now run the game open your saved game.
If the stats have not changed click the switch character button.