What is the most common cause for having diabetes in children? Type 1 or 2?

Type 1. Type 1 diabetes typically presents in a younger population while type 2 in an older. This is not always the case, though. As more children become obese, more are getting type 2, but most children who have diabetes have type 1. Conversely, most adults have type 2.
Immune vs obesity. The accepted common pathway in type one includes a simple infection, often a gut virus, that triggers production of antibodies that attack and destroy the insulin producing cells in the pancreas. Once destroyed the kid can't handle their glucose load it spills into the urine.Insulin must be delivered from injected sources. Age and excess weight in late teens or adults trigger type 2.