In today's Family Circus, we see PJ demonstrating his inborn ability to see the truth behind mundane appearances. Where the oldest son,** (presumably) the middle son,*** and the daughter**** see a cute little puppy dog, PJ sees a ravening beast with a Marmaduke/Antichrist-like tendency to swallow small children whole. The older siblings think they are steering their baby brother gently away from his delusions, but they are actually disrupting his heroic focus. PJ needs to be able to see the hell-beast for what it is so that he can slay it, tear out its beating heart, and devour it in a fetishistic ritual designed to augment his wilderness power and increase his efficacy against the monsters he will fight during his later career.
The Bear's Son is not only a medieval figure. However, we can see the specifically medieval content here in the intertextual Antichrist reference; Bil and Jeff Keane clearly know their Marmaduke. Christian texts make use of the Bear's Son, generally turning him into a type of Christ. PJ's vision here foreshadows the End of Days and the coming of the Beast. His family would be wise to heed his warning.
Of course, the comic could simply be incredibly stupid, but then why would anybody ever publish it?
*He occasionally expresses such knowledge by smashing most of his family's belongings and attempting to rape a woman, but I'm not sure PJ is quite at that stage yet.
**Destined to insult a little old lady and be eaten by a giant.
***Destined to insult a little old man and be ground into powder by a large eagle.
****Destined to be abducted by a troll, sleep with him, turn on PJ, and attempt to have him boiled to death in a crystal cauldron at the heart of a mountain frequented by the Fiend.*****
*****I am not making any of this up. I may be embroidering the details, but the motifs in question are sound.