Why do they grow so fast 😭😭😭

My 21 month old son is wearing 3T clothes already?! How did this happen?? I’ve actually noticed his 2T clothes not fitting him the best for a while now but was in total denial that 3T would actually fit him so well. He had some 3T outfits hanging in the closet and I reluctantly tried one on him the other day.. fit him perfect. I could’ve cried 😢 now we’re pulling out his old baby clothes preparing for his little brother who will be here in November and I’m staring at his little outfits thinking I feel like it was just yesterday he was wearing these. I think when his baby brother comes and i put him in one of his big brothers old outfits im probably going to be a big mess of tears.