Is there any precedent for a king who had a child with a member of a lower class, but not enough evidence to make them the heir?

Long story short, I've got a high fantasy story and I want the main character to be a king's bastard, but I want them to have a legitimate claim to the throne, or at least to make a claim to the throne. I've seen the bastard thing done before, but in the case of say Jon Snow, he's got no claim to the throne except possibly the fact that he's legitimate, which in my story the evidence of the child's parentage is too circumstantial to prove parentage. A king could have slept with a lot of people that week.<br><br>So is there any historical precedent for this?<br><br>Edit: To add a few details, the land is basically crusader kingdom, so has a strong religious bent, and making the claim public would probably have civil war level consequences