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.
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.
Superficially. Both tend to make the person tall and slender. Neither causes the other. Read more...