So Sheila says Emily is Bonnie's great great great great grandmother. Lucy says that her mother is the first cousin twice removed of Pauline (who is Sheila's niece).

Now we know the names of some Bennett's and the names and birth/death dates of others. Some we know absolutely nothing about.

Bonnie Bennett (1993 - present)

Abby Bennett (1972 - present) Bonnie's mother

Sheila Bennett (1956 -2009) she was barely a teenager in 1969 - so her birth date checks out - Bonnie's Grandmother

Pauline Bennett (unknown birth-unknown death) Sheila's niece

Joanna Bennett (unknown birth-unknown death) first cousin twice removed of Pauline

Lucy Bennett (unknown birth-unknown death) we do know she was killed at some point by Virginia St. John after 2013 when she gave her blood to get Bonnie out of the prison world (oFfscReAn!)- Joanna's daughter

Emily Bennett (unknown birth - 1864) - Bonnie's great great great great grandmother

Other Bennett's who are referenced in the show but we don't know where they fall on the family tree

Ernestine Bennett (unknown birth-unknown death)- her name is on a tombstone in Bonnie's dream in 3x12. Now this graveyard seems to be a hint to the blood knot spell that releases Esther from her coffin - which makes me think these are based on the generations of Bonnie's line based on the placement of Sheila and Amelia's tombstone's. So I do think she's an ancestor of Bonnie's

Marie Bennett (1880-1941) - her tombstone was seen in the Bennett graveyard in the finale of season 5. Based on her date of birth and death, I assume she was the Bennett witch that helped make the 1903 prison world. She would have been 23 at the time, so that makes sense to me.

Rose Bennett (unknown birth-unknown death) no reference to where her name was found, only that it was in 4x19. I assume this was in the graveyard scene, but I could not read those tombstones if I tried.

We know Sheila likely has a sibling since she has a niece. We also know Emily had more than one child because Stefan says that Damon saved Emily's children.

At first, I figured Ernestine would be Amelia's mom based on Bonnie's dream in 3x12, but Marie actually makes more sense as Amelia's mother based on her date of birth. So I made Ernestine Amelia's grandmother and Emily's daughter instead. I am also using Rose as Emily's second child. I assume both Ernestine and Rose were pretty young when their mother died since Emily looked quite young herself. This is just my personal headcanon tho. You can technically put some of these Bennett's anywhere in the family tree. All that's really set in stone is Bonnie, Abby, Sheila, Amelia, and Emily.

Now the most difficult thing for me is where Lucy's side of the family fits in all this. And I have 2 family trees based on where she could possibly be.

Here is my first family tree:

This is essentially the version of the family tree that the TVD fandom site gives us. I just made up names for some of the unknown Bennett's. Now, my only issue with this version is the huge differences in generations between Lucy and Bonnie.

Where Lucy is the great great great granddaughter of Amelia while Bonnie is the great granddaughter of Amelia. Which is very questionable because Lucy is clearly older than Bonnie. Even if there was a huge age gap between Sheila and her sibling, there would have to be a lot of very young pregnancies in a row in order for Lucy to be even a bit older than Bonnie.

I think I'm really pushing it with some of these dates since I had to make every one in Lucy's line a teen mom in order to make her 24 when she meets Bonnie.

Here is my second version of the family tree:

Now in this version, Lucy is Ernestine's great granddaughter while Bonnie is Ernestine's great great great granddaughter. Personally, I think this version works a little better.