If they were related, why would he send Harry to the Dursleys?

It seems like all pure-blood families were somehow related. While Harry was half-blood, his father was (apparently) pure-blood and transcended from a very old and powerful family. It is likely that Harry is related to Dumbledore from his father's side, although most likely very distantly.
It's also likely that he's distantly related to other pureblood families such as the Weasleys and the Malfoys.

but if he was related to the dumbledores jl rowling would have shown the family inter-relations like she has with the other family trees. True that pure blood families are all inter-related at some point but truthfully who knows?? but i agree with poseidon3...if dumbledore/harry were related why didnt he take harry in and raise him himself instead??

^^He had to go to the Dursleys for protection. Remember? It was in the Deathy Hallows, I believe. Harry and Dumbledore could have been related very, very distantly.

I don't think so... sure, there was something extra Dumbledore felt for Harry but I don't think they were ever related.

i don't know. I doubt it.

Harry being sent to the Dursley's had nothing to do with blood relations - he was safe there by the protection from his mother.

I thought all the pure-bloods were some how related (didn't Hagrid or Sirius say something like that?). Harry's related to Voldemort - he could just as easily be related to Dumbledore. It'd just be a distant relation, like how Sirius is distantly related to Molly.