royal blood

[queenimperiale]

Well, as an idea, maybe marrying a commoner (or a middle class- but during this time there wasn't one) and thus the family loses "points". But, as a random event, a royal historian found out that the wife/husband's ancestors were former Dukes/Duchesses of Suchandsuch. Not only would it give extra points later on, but relations between the current ruling family of the Duchy of Suchandsuch improves slightly.

 

[unmerged(19211)]

and you can always play the game as a complete bastard...

 

[The Regent]

Marrying a commoner could cause unrest in the kingdom. This unrest could appear in the form of a rebellion led by certain nobles. This would take place once the questionable child takes the throne, or immediately if the general unrest is already pretty high at the time of marriage. Having the rebellion being led by those 'greedy cousins' would be a cool twist.

Besides, a king in that time could always grant a title to the lucky commoner's father; therefore, making her a noble.