Impregnator Kings is a CYOA that originally started on pregchan back in December 2015.
You are Sir Edward, a medieval (ish) aristocrat who wants to become a King. Unfortunately, Edward is the son of a Duke and marrying into royalty would be marrying above his station. Fortunately, he has a fetish for impregnating women, and the seductive good looks and charm to pull it off. Edward has slept with dozens of women and sired even more children. His reputation for virility and potent sperm allowed him the opportunity to marry into several different royal families, all eager for an heir, as quickly as possible.
That is the basic premise. The actual threads they first appeared in have mostly 404'd, but the internet archive continues to have them. They can still be read and enjoyed here:
Thread #1: https://web.archive.org/web/20170619163636/http://pregchan.com/d/res/12251.html
This spans the beginning of the game when Edward selects his future bride, until Edward reaches Ruhemania and learns there's more to his new country than ever was hinted at.
1. Sir Edward of Virilia: The "you" of the story. He is fair-minded, and gregarious. Fond of outdoor activity and strength. He possesses a charming nature that attracts women to his bed, though some easier than others.
2. The Matchmaker: The young female aristocrat who introduces profiles of all available wives for Edward to choose from. He never learns her name.
3. Varillo: A mercenary who guides Edward through dense swamp and hills to reach Castle Valachia and begin his new life.
4. Ricardo: King Vlad's master of coin. A dismal old man, full of secrets. He appears to be King Vlad's only adviser, and one of the only other aristocrats in the castle.
5. Daniella: King Vlad's personal maid. Her position is independent of the servant hierarchy and subject to no authority but King Vlad himself. He has also given her blanket permission to do anything she likes, anywhere she likes. Tharja insists she isn't a spy, but just a busy-body maid.
6. King Vlad: The undisputed Sovereign of all of Ruhemania. Was originally an Independent Duke who fought a decades-long unification war to unite the various independent aristocrats in the country. Values obedience. The impalement stakes around the castle are a stark testament tPost too long. Click here to view the full text.