Todd:
His - Handsome
His face flushes bright red when you call him like that in front of the others, but he secretly loves it.
Yours - Love (only when the two of you are alone)
Neil:
His - Honey
The others snicker when you call him like that but neither of you care.
Yours - Beautiful
Knox:
His - Knoxie or Knoxious, depending on your mood
Yours - Gorgeous
Charlie:
His - Babe
Yours -Princess / Prince Charming
When he's looking for you, he usually asks others "Where is my princess / prince charming?".
Steven:
His - Meeks
Yours - Y/L/N
You love teasing each other about your last names so that's just how you call each other now.
Gerard:
His - Teddy Bear
You're the only person whom he tolerates to call him "Armpits" (as a joke, of course).
Yours - Sugar Plum