Schizophrenia and marriage. Affected?

Hello Doctor, My fiance's mother was diagnosed with schizophrenia at her age of 27. My fiance was 2 years old then. Her schizophrenia did not come from a genetic background. She was taking treatment but unfortunately she was not able to bear the brunt of the illness and she committed suicide about 20 years after she was diagnosed. She had mild borderline schizophrenia. My fiance and his sister are completely normal. The sister is 32 years of age and he is 31 years old now. My main query is that "is it safe to marry him?" Is there a chance he may develop the illness later sometime in life? Also even if he does not, is there a chance our future generation could somehow import those genes and get affected?