Hi!
I am looking for a movie (guess what..). Can anyone help me please?

It is probably from the 70/80s. It was not really a splattery movie but was somehow disturbing. Only details I can remember is that it was about two kids (probably brother and sister) that had some strange parents or uncle/aunt and they where this scene of them living under ground (like under their home in a dug basement). The scene was somehow disturbing cause if i dont remember wrong it involved the two parents/relatives actually eating human flesh or something similar.. and the two kids trying to escape..
Sorry for being so vague, but it's what I remember, i was a kid and saw the movie about 17 years ago ...
thanks for the crazy maniac that figures out something...