Dear customer, we fully understand your sensitivity about clothes fitting just right. For the 12 kg size you provided, you can choose the smallest size available in our product, which is the 3-4 Year Old option. However, 12 kg can look somewhat comfortable (flowing) in our patterns. To avoid any confusion and ensure a perfect fit that meets your expectations, we strongly recommend carefully reviewing our detailed size chart, which is available in the product images, and confirming it against your child's height and chest measurements. We thank you for your interest and wish you pleasant shopping.