Because there aren’t enough characters to boggle you already, you can marry your characters and then recruit their child into your army! They are very different from your other units because their growth rates rely on the growth rates of the mother, who can be different depending on the player’s choice. Children are tied to fathers in Fates , and will inherit from their mother their hair color , one of their classes , some growth rate modifiers , and one skill (that is at the bottom of the Equip Skill list). They will also inherit a class and a skill from the father.
A child’s growth rates, excluding their class, can be easily determined with some simple math. Take the stat you’re looking at, then add the growth rate from the child to the mother’s, and divide by two to find the average. That will give you the child’s base growth rates. So as you can see, you can increase a child’s growth rates, or decrease them, depending on the mother.
Skills are not inherited the moment the couple is wed. They will be inherited when you start the Paralogue and recruit the child. Move the skill you wish to pass down to bottom of the Equip Skill list to have control over the skill you’d like to pass.
As can be seen, the customization offered with children is endless. However, there are a few good rules of thumb to follow. First of all, if a father (and his child) are physically oriented (or magically oriented), pairing off with a magically inclined (or physically inclined) mother will not help your child’s Strength (or Magic), and may even hinder them in the area they rely on most.
In the area of defenses and Speed, the opposite applies. You should try your best to patch up poor Speed as often as you can, as Speed is one of the most important stats in Fire Emblem.
Finally, your Avatar is an amazing spouse gameplay-wise for everyone. The Boon and Bane you chose will factor into how the child (and Kana) will turn out, however, so plan accordingly.
To end this section, children are also very much unnecessary to the plot. You could play through the game and never marry anyone, or never complete Paralogues, and it will make no difference. This is especially relevant to Conquest players given the limited space of time to build supports. If you miss out on a kid or ten, don’t worry. They most certainly help but are not needed.