A three-piece suit for a 9-month-old boy typically includes a jacket, pants, and a vest, designed for both comfort and style. The jacket is usually made from soft, breathable fabric with a gentle lining, featuring buttons down the front and sometimes a small pocket. The matching pants are elasticated for easy dressing and a comfortable fit, allowing plenty of movement. The vest, also coordinating with the jacket and pants, adds a touch of sophistication, with a simple button closure. This ensemble is perfect for special occasions, combining elegance with the practicality needed for an infant.