Two twin brothers both called Antipholus; two twin servants both called Dromio; all ignorant that their twin resides in the same city as them. It’s a recipe for mayhem and comedy, as one is mistaken for the other by everyone including their own wives.
Shakespeare based the plot for his comedy on a farce by Plautus, scaling up the mayhem of the roman original to create a work of furious slapstick and social nightmare.