No "dragonkin" in the FRCS.
Half-dragons in MM1, but I'm guessing that's not what you mean.
Dragonspawn (Black, Blue, Green, Red, and White) and Draconians (Aurak, Baaz, Bozak, Kapak, and Sivak) are both in the Dragonlance Campaign Setting. Might it be one of those ... ?