If my parent had a stroke, what do I need to do if middle aged?

Check blood pressure. It would be best to know what kind of stroke: bleed vs ischemic, any other causes of your parent's stroke, age at which the stroke occurred; then focus on your risks for stroke, particularly high blood pressure.
A few things. You need to do what anyone else without a history of stroke needs to do : control blood pressure, control blood sugar and body weight. Make time for regular exercise and see your doctor for routine preventive care. These are the best methods for lowering your risk for stroke, heart attack and vascular disease.