Among one of the new features introduced in Fire Emblem: Awakening is the possibility of further developing the support relationship between characters of different sex: achieving a Support relationship of level S will make them marry and let you use their children as playable characters in your unit.
There are a total of 13 children available in the game which can be acquired in Paralogues and Side Missions, appearing after the corresponding mother gets married. Childrens will start joining you after Chapter 13 has been completed.
Pleane not that only certain marriages will give you children and the parents’ stats, skills and classes will deeply influence their abilities so make sure to take good care of all the possible parents. Not getting any of these children will not only deprive you of possible strong units in battle but it will also prevent you from accessing most of the game’s Paralogues.
There’s also no chance to miss the Paralogue mission where you’ll be able to recruit the children: after two characters have married their corresponding Paralogue chapter will appear on the world map after chapter 13. Because of this there’s no need to give any of the character the support relationship of level S before this chapter, except for Chrom, who’s going to get his first children during Chapter 13, no matter what.
Also note that both Chrom and your Avatar have the ability to have two children; all childrens will join you at level 10 and can reach a relationship level of S: however, they can only have children if married to your Avatar. Also, all children will start with a C relationship rank with both their parents.
Children will get their parents’ last equipped skill except for Chrom’s children who get the Rightful King skill. Using this feature will allow you to create some interesting combinations and create some devastating units, taking the best features of their parents.
Kjelle is Sully’s children and her available classes are Cavalier, Myrmidon, and Wyvern Rider but she can also become a Knight. If you make Sully Chrom’s wife you obviously won’t be able to get Kjelle since Lucina will be her daughter. If you want to get Kjelle make sure that you don’t make Frederick or Stahl Sully’s husband if you want to have more class choices. Making Donnel Sully’s husband will allow Kjelle to access 7 basic classes with 6 of them being physical oriented classes. Donnel is also very good for other wives so you may want to choose some other husband for Sully.
Article from Gamersyndrome.com