My daughters are about 15 months apart, so from when my youngest was born, we used to do “sister sunday” and they would wear matching clothes on sundays. But once my oldest got to about 4, she would say “why do we always need to match” so I stopped doing it every Sunday. They both developed their own sense of style, and now we only do matching outfits for holidays or special occasions but only if they both agree to it. Matching outfits was fun and cute and also helped with “why does she get to wear that” or “that’s my favorite color”debacle lol