welcome to healthcare magic,
if you have a family history of diabetes
then yes they could be chances your children could be suffering from diabetes because of the symptoms expressed.
you could get a blood sugar test done to rule it out.
another thing is they could be having a high metabolic rate so whatever they eat gets used up easily thats way they have to eat frequently.
third issue could be the weather. they could become dehydrated due to the hot weather.
hope to have answered your query