Virgil:
You for him~Virge, Storm-cloud, or (as a joke) Sunshine
Him for you~ My other half or flower

Roman:
You for him~ Princey, Ro, or you like calling him Princess as a joke sometimes
Him for you~ Princess/Prince or Love

Logan:
You for him~ Logie bear or Lo
Him for you~ Star or my only emotion

Patton:
You for him~ Cuddle bear or Sugar
Him for you~ Puppy or Honey Cake

Deceit:
You for him~ Snakey or (to make him blush) Pumpkin
Him for you~ Hun or (to make you blush) Hotie

Remus:
You for him~ Stinky, 'Mus, or (for fun) Love Muffin
Him for you~ Boo or Sweet Cheeks (he's not taking about your face cheeks though...)