So I decided to play a game as Castile, and get some achievements. The game has been going well so far, I have a foothold in morocco, I have Guyeene as a vassal and I have control of most of portugal. This is where the problem came up, my ruler died with my heir being too young so I got a regency council. Then i got one of the events where you have a 50% chance your heir dies if you pay some money. I did it and unfortunately my heir died. So now I have no heir, with an Interregnum. I have never seen this before so I don't know if I will ever get another ruler in game.