Is xxy klinefelter's syndrome related at all to marfan's syndrome?

No: Klinefelter syndrome is a group of features seen in some males with an extra x chromosome (they are xxy). A klinefelter syndrome male tends to be taller than expected compared to his father and brothers. Klinefelter syndrome is not related to Marfan syndrome.

No: The two syndromes have some similar features, but they are different syndromes that are unrelated. Klinefelter syndrome is caused by ahaving at least one extra x chromosome in a person who has a y chromosome (normal male=46 xy, klinefelter=47xxy). Typical Marfan syndrome is caused by a mutation in fbn1, coding for fibrillin-1.