Another topic spoken against Finnceline is age of the two. Finn (as of Season 4) is fourteen years old while Marceline is over a thousand years old. But according to Andy Ristaino, Marceline was between the age of 18 through 21 when she was bitten. Even though she is over a thousand years old, she technically is still that very age she was bitten. Because Vampires in general never age and Finn does, this might cause Marceline to have feelings for Finn when is around the age she was bitten later in the show.