uhm..
seeing the years...
I thought that one are Vincent parents .__.
Genealogy trees usually go up-down, so not his parents. His parents are higher, there we can read Claudia (Ciel's grandmother), but going down the tress's bisected again when it comes to Vincent's and Rachel's descendants. Like I've said a lot of times... There's another child in the Phantomhive family!! Ciel's twin brother! (=・ω・=)
Here's a quick drawing:
http://www.hostingpics.net/viewer.php?id=228651image230.jpg
The branch is clearly splitting.
so... what do you mean is, ciel has a twin brother?
Seeing all the posts about the twin theory I decided to reread from the start. It's almost certain that the Ciel we know is not the real Ciel! The family tree panel now makes sense, there are two branches coming from Vincent's name http://www.mangago.me/read-manga/kuroshitsuji/an/kuroshitsuji/103/pg-5/