Can Monster Reborn be used on fusion cards?

As long as the Fusion Monster was properly Special Summoned (by Fusion Summon normally, but if the monster cannot actually be Fusion Summoned, then by following the text on its card) then you can bring it back using Monster Reborn.

Some may say "This card cannot be special summoned except by Fusion Summon" which means even Monster Reborn can't be used, even if it was summoned properly.