Co leads means there are two characters/actors sharing in all the heavy lifting, that the story requires that both of them have as much narrative pull as the other.
Booth and Bones
Ichabod and Abbie
Red and Liz
Castle and Beckett
Dean and Sam
Those are characters that are co-leads.
OUAT is not a co-lead show. There are some actors that get more screen time (Emma, Regina, Hook) but the show is not billed a single lead with a supporting cast (House, Arrow) nor as a co-lead (Bones, Sleepy Hollow, Castle, Blacklist, Supernatural) but as an ensemble show (Grey’s, HTGAWM, TBBT, Chicago Fire)
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"He was a lot of things to me" "The only conclusion was love"