The narrator brings us back to when Luke was six and built up the courage to ask his mom why he had to hide.
Short story: Luke's existence is one big violation of the law.
As a kid, Luke thought that once he grew up to be big like his brothers, he wouldn't have to hide anymore.
When Luke's 6th birthday came around, he started to rethink this hypothesis. Days later, Luke realized (and his mother confirmed) that Matthew and Mark never had to hide to begin with. The truth comes out!
Luke's mom told him that, at the time, the new formed Population Law said families could only have two kids. And being child #3 meant that her new baby would have to be kept on the down-low.
Originally, Luke's mom thought that the whole Population Law nonsense would blow over and not be an issue by the time Luke was born. Yeah, not the case. It actually got worse.
The TV (which Luke isn't allowed to watch for some reason) started talking about the Population Police who go to extreme measures to enforce the law. Very Nazi-esque.
After that, Luke didn't mind playing a perpetual game of Hide and Never Seek. He even tried to find a silver lining like not going to school, hanging out with his mom, and always have their backyard protected by the woods.
The same woods that government just started tearing down.