My twins are now 7 and choose most of their own clothes, somethings they choose are completely different ( their bathers) others are the same, but different colours, others are identical, I dont dress them, or pick their clothes in the morning, but probably 80% of the time, they have at least one item the same ( same skirt, diff tshirt) and the rest of the time they have exactly the same, so I let them do their own thing, its their choice at this age how much they want to play on the "twinness" they have, IYKWIM.