Is the uncle that watches over their house related to them? and how? so confusing...

Zach owns the Salvatore Boarding House and is a descendent of Damon and Stefan Salvatore, referring to them as 'uncle' when in private. He is also human.

Zach really isn't their uncle...its just that because they're stuck being young and he looks older that they call him "uncle". He is related but he's like their great great(maybe more greats) grandson

his not really the uncle he is one of there desenents he just looks like their uncle because damon and stafen never age and he is a human so it also means that no other vampire can come in umless invited or untill the human dies x