My Brother, Age 55, Has Been Having Strokes. He Is

My brother, age 55, has been having strokes. He is on blood thinners. He was just told they're not due to heart condition, but caused by a blood condition, which is hereditary.
He also had a PET Scan which revealed multiple "spots" in his lungs. He didn't actually call it cancer.
My question is: Do you know what blood conditions would be causing the strokes and/or the growths in his lungs?