In case you were also wondering what a "fourth cousin" was, someone who shares a pair of great-great-great grandparents[0]. Wikipedia has a great set of diagrams[1] in case you're also confused about first, second, or third cousins. I figure through induction you can presume any nth and nth removed from that page (I foolishly thought 3rd was where people arbitrarily stopped keeping count....)
[0] https://www.reference.com/family/fourth-cousin-7b40e096c6d65...
[1] https://en.wikipedia.org/wiki/Cousin#First_cousins