Can a kinged piece jump another king piece?
As was indicated by @JaysonSmith, a king can always be jumped by another king. This holds for any variant of draughts/checkers.
The privileges that a king obtains differ by variant, however.
- backward movement: in all variants, kings can move backward, but men cannot.
- backward capture: in all variants, kings can jump backward, but men cannot for American/English checkers/draughts, Italian, Spanish, Czech and Thai draughts.
- long range movement and capture: a king can move and capture long ranged (like a bishop in chess) for International, Frisian, Russian, Spanish, Czech and Thai draughts, as well as for Pool checkers, whereas men are short ranged in all variants.
- invulnerable being captured by men: a king cannot be jumped by men in Italian draughts.
Yes, a kinged-piece can certainly jump another kinged-piece. In fact, having a kinged-piece does NOT make it invulnerable to being 'jump'. This means that even a NON-kinged-piece can jump a kinged-piece. The only advantage to kinging a piece is that it is able to move both Forward and Backward. A non-kinged-piece can be severely limited in jumping due to this rule. Thus, if a non-kinged piece were in position to jump three opponent's pieces in a row, but the second jump required the non-kinged piece to jump backwards, the non-kinged piece would have to resort to only jumping the first opponent's piece.