As in Harry Potter, when people can be born into strong magical families but have no magic themselves, the galaxy is shocked and, in some cases, angry when the boy born into the Skywalker family - stronger than any before them in the Force - has no Force sensitivity at all. There's nothing Han or Leia or Luke can do - Ben simply isn't sensitive.
Though the family love him unconditionally, Ben feels more and more resentful as he grows up around people immersed completely in the Force, and he can't feel a thing. Things only get worse when his cousin Rey is born, almost as strong in the Force as their grandfather. That's when Snoke starts whispering in his ear.
+ Leia and Han still send Ben to Luke, to train in combat and hopefully find peace with who he is
+ Rey is too young to understand why her cousin hates her
+ The First Order use Kylo as a bargaining chip - they have Han and Leia's son, so they better do what they say
+++ When they get tired of using Kylo, the Order turn their attentions to Rey
Gen, Skywalkers, AU - Kylo isn't Force sensitive
Though the family love him unconditionally, Ben feels more and more resentful as he grows up around people immersed completely in the Force, and he can't feel a thing. Things only get worse when his cousin Rey is born, almost as strong in the Force as their grandfather. That's when Snoke starts whispering in his ear.
+ Leia and Han still send Ben to Luke, to train in combat and hopefully find peace with who he is
+ Rey is too young to understand why her cousin hates her
+ The First Order use Kylo as a bargaining chip - they have Han and Leia's son, so they better do what they say
+++ When they get tired of using Kylo, the Order turn their attentions to Rey