How does someone else know from here they are related to me through my grandmother and are cousins?

DeborahBoyles

I am not sure where I ask this question so I will write here. I had a person from facebook message me saying that we are 5th cousins. How do I see that we are related as he did? Thanks for your help.

Áine Ní Donnghaile

@DeborahBoyles

You can see the details of the campaign here. https://www.familysearch.org/en/connect/787b5034-edf8-465c-b6fa-f301452de294