Bastard-born children were fairly common.
But they aren't nobles. And within the scope of this game, it doesn't matter if, in real life, bastards sometimes inherited. Within the scope of SMA, it's generally accepted that the idea of base-born ascending to nobility is ridiculous. If you dispute this, I encourage you to ask, IC, in any realm in Dwilight if a commoner can become a noble.
I digress. This isn't directly related to the topic.
Then they are foolish because it definenently happens on Dwilight. Game mechanics trump roleplay and game mechanics say its possible.