Playing as a mage, I married the frog princess for the +3 Intellect bonus.
She forced me to have kids (otherwise she turns back to frog ) , and I got Neiron (+5% xp per combat) , the second son gave me +10 rage, and the third +5 defense.
These bonus would have been nice for a Warrior, but as a mage, they are not so great, so I divorced the frog early, to minimize the loss of gold..
Next wife will be probably the demon wife, but I will not give her any child so that I can choose my weapons
