Unfortunately having one medical condition doesn't foreclose on getting another one. So yes it entirely possible for a CAH child to get Diabetes type 1.
However the thirst could also be CAH related such as florinef dose or electrolytes being out of whack.
Remember there is also another kind of diabetes called Diabetes Insipidus where the anti diuretic hormone is at fault. Usually accompanying this form of diabetes is a huge thirst, as well as, the excretion of large amounts of very dilute urine similar to Diabetes Mellitus.
An acidotic breath (smells a bit like nail polish remover) often accompanies Diabetes.
