We're sorry to hear you experienced leaks at night. Size and fit are a huge part of finding the right diaper for your grandson. As you know, babies come in all different shapes and sizes so diapers fit every baby differently. Our diaper sizes are organized by weight, and since no two babies are the same shape you will notice some overlap between sizes. In most cases, your grandson should be within the weight range for the size you are using, but we've found that about 30% of babies are in the wrong diaper size. Please call us at 1-833-646-5262 for assistance. We're happy to help you.