Craster's Keep functioned as a sanctuary for the Night's Watch, but it came at the cost of the crows having to tolerate how Craster 'married' his daughters and continuously bred children from incest. What do the White Walkers do with the babies that Craster gives them? They turn them into more White Walkers.
The White Walkers want life from male babies. Since they're babies, the Night King can change them into White Walkers (his army generals) and train them as they grow up. Craster's sons were given to the White Walkers, and inturn the White Walkers protected him from wildlings and left him alone.
All of Craster's sons that were turned into White Walkers would die when the Night King died. If they take some time to grow up, they won't be growing up. They died when he died, no matter where they are.
Craster gives his sons to the White Walkers in exchange for the safety of his keep, the security of his life and of his daughter-wives.
Seclusion. For the next 8,000 years, the White Walkers remained in seclusion in the far North, where some fans think they spent that time in some kind of slumber or hibernation. To quote another fantasy epic: “History became legend.
Game of Thrones: Season 4
The baby becomes a White Walker.
Either way, it's all down to selection bias. The White Walkers were made from men. The vast majority of humans they encounter are men or boys, and as Game of Thrones keeps reminding us, old patterns are hard to shake off. This doesn't mean we'll never see any female White Walkers in Game of Thrones.
A Feast For Crows
However, Jon Snow, the new Lord Commander of the Night's Watch, has swapped Gilly's son with Dalla's. This is done to spare the innocent child from Melisandre's flames on account of his king's blood, leaving Gilly's son at the Wall.
The White Walker might have recognized his cowardice as surrender and therefore let him live. It is possible that the creatures wanted more than just to kill the living. They wanted subordination.
The First Men were destroying the sacred forests, and the Children believed they needed stronger protection. Sadly, the White Walkers turned against the Children, and became the fearsome force we've all come to know now.
All of that changed when Bran entered the picture as the Three-Eyed Raven. This introduction gave the Night King a true motive outside the typical megalomania of Big Bads. By wiping out the Three-Eyed Raven, he would be wiping out all memories of the previous world and fully ushering in his new era.
According to Old Nan, the Night's King may in fact be (hold on to your small clothes) a Stark! If that isn't enough, legend has it that the Night's King was not just any Stark, he was King Brandon Stark's brother—or possibly Brandon Stark himself!
As for why babies, and not adults, are candidates for transformation into White Walkers, this is likely because infants are easier to mold into whatever the Night King wishes.
Biography. The Night's King and the Night's Queen enslaved the black brothers and performed human sacrifices. According to legend, the Night's King was originally a Lord Commander of the Night's Watch who found in the Haunted Forest a cold woman with bright blue eyes, seemingly a female White Walker.
No, the Night King is not a Targaryen.
In the books, however, the story of the Night King is slightly different. The Night King isn't the leader of the White Walkers. Instead, he's a legendary historical figure who supposedly betrayed the Night's Watch to marry a “corpse queen” and then crowned himself a king.
A young wildling girl who lives north of the Wall, Gilly is one of many daughters of Craster, a wildling who takes all his daughters as wives once they grow up into women. She has a son with her father Craster. Samwell falls for her and becomes protective of her.
According to a recent Game of Thrones fan theory, Samwell Tarly might be Jon Snow's brother and the last missing Targaryen with a claim to the Iron Throne.
4) Sam and Gilly hook up in slightly different fashion
Sam and Gilly do have sex in the books, and it is after the death of Aemon.
So the basic thrust here is that, according to fan theory, the current Starks may be descended from White Walkers, thanks to a child born of a human man and a White Walker woman known to legend as the Night's King and the Night's Queen respectively.
The reason why Arya was able to appear out of nowhere and kill the Night King was that she was able to disguise herself as a wight and lead all the White Walkers into believing that she was part of their army.
The revelation in this House of the Dragon episode suggests Aegon Targaryen knew about the White Walkers, and that was why he conquered Westeros in the first place.
The collagen spacing of their “winter eyes” reflects blue light, making them appear an eerie blue.
When Tyrion announced his support of Bran being made king, he said Bran had the best stories. The world at large took that literally, and started listing every character that had better stories than Bran.
The ultimate goal of the legendary White Walkers was the end of every living thing in existence, which they planned to achieve by killing the Three-Eyed Raven and creating an endless winter to eclipse the known world.