I have a Kyurem(White) in my Pokemon White 2. It is currently Lv. 81. If I decide to defuse it back to a regular Kyurem and a Reshiram, will both of them have levelled up, or only Kyurem? Here's my problem: If it's fused, it's still called Kyurem.
Kyurem will be the Pokemon that levels up, not Reshiram. Almost everything belongs to Kyurem when it fuses, Reshiram somewhat ceases to exist when fused.
Hope I helped!