When they call for bondage, try clicking on different options. If you always choose the same one, you'll get that kind of family. Ex: if you always choose the artistic option, you'll get an artistic family.
If your family is like this, for example..... Mametchi, chantotchi, and memetchi, and you marry mametchi to another chantotchi, you get a blended family UNLESS mametchi's bonding is up to 100%. Does this make sense?