XXY syndrome is also known as Klinefelter syndrome.
In this syndrome, the male is born with an extra copy of the X chromosome.
In normal cases, males have XY chromosomes. Due to improper segregation of chromosomes, they become XXY chromosomes.
XXY syndrome affects testicular growth resulting in smaller testicles, which can lead to low production of testosterone.
This syndrome also causes facial hair growth, low muscle growth, and enlarged breast due to one extra X chromosome.
In most cases, men with Klinefelter syndrome have no sperm or little sperm.
XXY condition in men has less testicle growth and low production of testosterone, it is a condition of no sperm or less sperm that is why they don't have babies.