Note: I'm not a lawyer and I don't play one on the Internet. Seek legal counsel if you have serious copyright issues you wish to pursue legally--but remember--it ain't cheap.
I realize that they are "your" ancestors and you probably have some emotional attachment to them. That's perfectly normal.
You may also have some emotional attachment to facts that have taken you a long time, some money, and a great deal of time to ascertain. Let's say that you "discover" that Johann Schmitpluffer was born on 12 August 1739 in Gottareallylongschmirkingname, Germany, the son of Erasmus and Anna (Umlautholder) Schmitpluffer.
You decide put those facts online, perhaps including your analysis along with those facts. It is a very long and detailed analysis, reflecting your research and your own creative way of writing up the analysis. Creative here meaning that your prose is eloquent, engaging and keeps the reader on the edge of her seat. We do not mean "creative" in the sense that you made it all up.
Your distant cousin from Bangor decides to use the fact that Johann Schmitpluffer was born on 12 August 1739 in Gottareallyloneschmirkingname, Germany, the son of Erasmus and Anna (Umlautholder) Schmitpluffer in his genealogy database, his blog etc.
Oh, your "taters are irked." You fly off a nasty email--it is not eloquent and it is not engaging. He has used "your" information and he needs to pull it.
Sorry, it's not your information. It is a fact and you have no more right to use that fact than anyone else.
Your distant cousin from Seattle decides to copy all your eloquent, engaging prose and use it in its entirety in her own material. The Seattle relative does not give you one whit of credit. That's a problem and that's a violation of your copyright because your paragraphs of writing were used. Whether you can get the Seattle resident to remove their material or cease from using it is another story. You can try and convince them nicely to remove the paragraphs of your writing, but they may choose not to. Enforcing your copyright may not be easy and if you decide to hire lawyers it certainly isn't cheap. You may contact the ISP or the web host that houses the information and prove that the prose is yours. You may get lucky and they may remove it.
And if your cousin in Seattle removes the prose and replaces it with:
Johann Schmitpluffer was born on 12 August 1739 in Gottareallyloneschmirkingname, Germany, the son of Erasmus and Anna (Umlautholder) Schmitpluffer
There's not a lot you can do.
