The Beast being illegitimate has been a theory for ages, even for the Disney one.
Well, considering that it says the 'queen' bore a son, it would imply that this woman was, if anything, likely a concubine. Usually, the currently ruling queen's offspring with the king would get the throne.
Though, this also depends on this woman's social status. If she was a powerful princess from another nation or so, children of hers and the king might still have a right.
No, this is from a time, when marriages were arranged for political reasons. Children were produced for heritage. For love there was a concubine often more than one also with children but with less power. Just getting a smaller title. just Google Ludwig XIV.
Ohh look, it's his mother! This scene is going to be fun, isn't it? And oooh, that's awkward. The king now has a legitimate heir to the throne, which means that Argus's chance of inheriting, which were already slim, just went down to zero. Argus's mother is definitely upset about that, and Argus himself doesn't look happy at the news that he has a baby brother. In his defense, though, I think he's more surprised than anything else.
Also, when did December creep up?! I'm on a countdown to whole pile of life-altering stuff and now it's really starting to loom!