Mouvar's Magic: Piers Anthony and Robert E. Margroff

Kelvin of Rud V. As soon as the vile witch Zady has grown herself a new body, Professor Devale sends her back into the frame to flush out Mouvar and the Opal - and kill everything Kelvin Knight Hackleberry holds dear. But growing a body has taken Zady twenty years and by now Hackleberry is almost a grandfather. His human son Charles is in love with Glow, nursemaid to the slow-growing twins Kildee and Kildom. His dragon son Horace is in love with another dragon, Ember, equally telepathic. And although his daughter Merlain doesn't know it yet, her true love, whose name is Glint, is just about to come into her life - unless Zady gets to him first. The stakes are high. The last battle is on.