It is a commonly seen phenomenon that type 2 diabetes runs in families. That is why we ask for family history for diabetes when we suspect diabetes in a patient. There are multiple genes along with environmental factors involved in this and the exact pattern of inheritance is unknown.
As for type 1 diabetes there is also thought to be a genetic predisposition, but Type 2 diabetes has a stronger genetic basis.
Fun Fact: If you are a woman with type 1 diabetes and your child was born before you were 25, your child's risk is 1 in 25; if your child was born after you turned 25, your child's risk is 1 in 100.
If you have type 2 diabetes, the risk of your child getting diabetes is 1 in 7 if you were diagnosed before age 50 and 1 in 13 if you were diagnosed after age 50.
Source : http://www.diabetes.org/diabetes-bas...-diabetes.html