This might be a long shot, but...
What if the "depending on the combination of the married characters, the two will give birth to a child" is referring to same-sex couples not being able to have children?
If what this says explicitly is true, then some couples, after marrying, won't have a child/children? That could also mean that some characters would be like Anna, Gangrel, etc. from Awakening, not having any specific child (ex. Say'ri marries Lon'qu, and they have no children).