Yeah i agree with Haphazard: it usually takes only a few years for your new king to marry an aristocrat. I wouldnt use cheats though - the game is more fun without them.

I remember when i played English i had a king who ONLY produced daughters (like 7 of them) - it was so frustrating cuz my succession wasnt secure. So i could have faced a Civil War. In the end the last kid that he had was a boy who became the new ruler of English Empire.