Do people today with a disease caused by single gene mutation that is inheritable - all share a common ancestor? First question here so sorry if it is about both genetics and evolution.

So, if I get a disease which can be clearly identified on the gene level and all my descendants inherit it, after 500 years do all people with the disease share the common ancestor (given that it's only inheritable)?

I mean, my clear guess first would be "yes" but I really want to check it since I haven't read it anywhere.

Feel free to post materials on this too.
Thanks!
That can happen, but it's more likely that the disease will be present in more than one family. Diseases with a single, small genetic cause will be more likely to flare up elsewhere (assuming the disease isn't too bad, and it wouldn't be if it's been in the family for 500 years).

However, what you will find is that in your family that disease is almost always present together with some other inherited genetic feature that is nearby on the genome (i.e. an inherited haplotype block). This association is less likely to be shared with other families.