Familiars that follow behind Isaac have a certain priority in how close their position is to him over other familiars, with Little C.H.A.D. having the lowest priority at 6th and thus being farther from Isaac than familiars of different priorities.
Synergies
BFFS!: The familiar drops hearts in a repeating pattern of 2, 2 then 3 rooms.
This item is a reference to the C.H.A.D. boss from Super Meat Boy, where after defeating C.H.A.D. he becomes very small and in the following cutscene will keep trying to get kisses from Meat Boy.
Little C.H.A.D. will blow a kiss to the camera every time a room is cleared, even if no half red heart is created.
Half Red Heart every three rooms.
C.H.A.D.
Familiars that follow behind Isaac have a certain priority in how close their position is to him over other familiars, with Little C.H.A.D. having the lowest priority at 6th and thus being farther from Isaac than familiars of different priorities.
BFFS!: The familiar drops hearts in a repeating pattern of 2, 2 then 3 rooms.
???, 
Tainted ???, 
Dark Judas, 
Tainted Judas, 
Tainted Forgotten: Useless, unless 
Apple of Sodom or 
Dark Bum have been collected, since these characters can't pick up red hearts.
Keeper/ 
Tainted Keeper: Will give Blue Flies instead of hearts, acting as a weaker 
Rotten Baby.
The Binding of Isaac: Rebirth
