Hmmm...
Probably
Homeland
Spellfire
And then, the third would have to be a trilogy as it really isn't complete without being a trilogy...
Which would be the
Dragonlance Twins trilogy (or Legends Trilogy). If I had to choose one of those it would probably be Time of the Twins as my favorite, even though you don't get to the end of the trilogy with just the first book.