In Fates, children are linked to male characters - apart from Kana, who is always Corrin's child, and Shigure, who is always Azura's child. Like in Fire Emblem Awakening, you can recruit a child character once the parent they are connected to reaches S Rank support with someone. The route you choose will also dictate which child characters you are able to recruit. ⁶ Reina is a permanent character in Birthright but a temporary character in Revelation. This does not happen in any other routes. ⁵ Kaze will leave at the end of chapter 15 in Birthright unless he and Corrin have a support rank of A or S. It can be Puppet A, Puppet B, or Puppet C. The earliest this can happen is chapter 22. ⁴ Yukimura is recruited in the Castle once you have a level three Puppet. The earliest this can happen is chapter 18 in Conquest and 22 in Revelation. ³ Flora is recruited in the Castle once you have a level three Ballista, Fire Orb, or Launcher. The earliest this can happen is chapter 18 in Birthright and Revelation, and chapter 22 in Conquest. ² Fuga and Izana are recruited in the Castle once you have a level three Hot Spring. Male Corrin will recruit Felicia in chapter six and Jakob in chapter 15, and the reverse is true for Female Corrin.
¹ Jakob and Felicia are recruited no matter what, but the order depends on your gender.