The Secret Gilbert ~Klaus Mikaelson LS~

Everyone knows the one and only, Elena Gilbert. We all know that Elena has a younger step-brother/cousin Jeremy, but what if there was another Gilbert sibling no-one even Elena or Jeremy themselves, knew about? What happens when Katerina, Eliza, Gilbert Warren, the long lost Gilbert, comes back to her home town Mystic Falls searching for, her blood sister Elena. Will she tell anyone, who she really is? Is she human? What happens when she meets her Mikealson?
I do not own the vampire diaries or any other character except Katerina, Eliza, Gilbert Warren.