They are boys and generally speaking boys tend to have fewer medical issues than girls.
That doesn't make any sense !!!!
The health disparity between males and females begins during fetal life and continues from cradle to grave. About 115 males are conceived for every 100 females, but males are much more likely to die before birth, so there are only 104 newborn boys for every 100 girls. Boys are about 60% more likely to be born prematurely, to have conditions related to prematurity such as neonatal respiratory distress syndrome, and to suffer birth injuries. Boys are about 18% more likely to die before their first birthday than girls.
When it comes to health, males are the weaker sex throughout life.