Kindred

"Kindred" refers things, thoughts, feelings, or especially people, that are in some way related or have significant similarities (usually re: ideas or experiences, not in appearances).

--Related--
"I'm going back East to visit my kindred on my mother's side of the family."

--Significant Similarities--
"We felt a special connection when we first met; we soon realized we were Kindred Spirits."

"This group of documentaries have a kindred theme."