I was trying to figure out why the fairy babies would not only burst out of their mother in so gory a fashion but be mindlessly carnivorous off the bat, then it came to me.
The fairy becomes pregnant, (anyone know the gestation period for fairy hybrids?) but continues adventuring with the party, afraid to leave her love, and possibly even keeping the pregnancy a secret, afraid to tell the mate and make them worry. Deep in a dungeon, the party is caught unaware by a ghoul. Unable to get her voice loud enough to warn her mate, the fairy does the only thing she can do, and distracts the undead herself.
off the charts Level drain, DM fudges fort roll failures, fairy dies valiently, her now widowed mate smiting the everloving fuck out of the beast that slayed her. The PC, being a loving caring sort, faithfully carries her tiny body out of the dungeon, most likely to either bury her or return her to her family/homeland. As the PC RPs the last caress of her frail frame, a final kiss, there comes a disgusting SQUELCH from her flesh. The widowed scarcely has time to feel the pain of seeing their love explode so horribly before they have no choice but to run like mad from the groaning, twitching, level-draining cloud of infant fairyghouls.
For maximum effect, leave them semi-sentient/hiveminded, so they can groan "Daaaaadddyyyyyy" in unison as they come to hug their father to death.