Why do 47xxy people have difficulty having children?

Genetic dysfunction: 47 XXY is a genetic condition that sometimes can cause hypogonadism and developmental delay. For those planning families, it's important to remember that there is a split of the x and y chromosomes in the sperm, and usually it's an equal split, some with x and some with y. With 47xxy, a lot of sperm, 2/3 most likely, will have either xx or xy, leading to non-viable sperm-egg combinations.

Klinefelter's : Syndrome patients, 47 xxy, have an extra x chromosome, one of their nain problems is diminished main sex organs (testes) function, hence diminished production of healthy sperms, although testosterone can help with sex characters development, they still can't reproduce on their own, assisted fertilization can help in some cases, expensive though