Is Jeremy related to Katherine?

he's not ...

i think Katherine related with Isobel which is Elena's mom ...
i guess that's why Isobel know her :)

Yes Elena is related to Kathrine and Jeremy is Elena's cousin

No. Katherine is Elena's great great great great great 'etc' grandmother on her MOM's side (isobel) Jeremy is Elena's cousin on her DAD's side (John). Just think... Is your Grandmother on your mom's side related any of your cousins on your Dad's side?

probably so beacuse elana's dad is his uncle and katherine and elan are related

Jeremy is not related to Katherine because he is not Elena's biological brother.

Actually, they are. I mean Elena is Jeremy's cousin, and Elena is obviously related to Katherine. So, it's only logical that Jeremy too is related to Katherine in some way.

He is actually since Katherine is Elena's Ancestor and Elena is related to Jeremy so Katherine is Jeremy's ancestor too.I rest my case LOL

i dont think so !

Sort of. Elena is Jeremy's cousin and then Katherine is Elena's doppelganger and THEY are related. They're related by a long line of blood. Because Uncle John is Jeremy's uncle and John gave birth to Elena.

well regardless that he's not elena's real brother, i think that Jeremy is still Jeremy Gilbert, and all Gilberts are sorta discendants of Kather

Yes his is because he is related to Elena and Elena is related to Kathrine.
He is related to her distantly.