If joe has the marfan syndrome and has a child some day what are the probaliblities that his chaild will have marfan?

There is a 100% probability of his child having Marfan's syndrome.

The syndrome is carried by the FBN1 gene, and is dominant so there is no way to avoid having the disease. However the severity of it may vary from mild to severe, so his child may suffer from a mild form of the syndrome.