What is a fourth cousin?
A fourth cousin shares a set of third-great-grandparents (great-great-great-grandparents) with you. Your parents are third cousins, and your grandparents were second cousins.
Preset to this relationship. Change the steps to compare with neighbouring relationships.
They are your
fourth cousin
Common ancestors: your great-great-great-grandparents. Expected shared DNA: 0.195%
Shorter branch = 5 steps → 5 − 1 = 4 → fourth cousin. Branches differ by 0 → not removed.
Fourth cousins share about 0.2% of their DNA on average (1/512). Many genuine fourth cousins share no DNA segment large enough for a test to detect, while others share a small segment by chance.
The shared ancestors usually lived five generations back, often in the 1800s for people born late in the 20th century, so census and parish records are the usual way to confirm the link.
Your fourth cousin's child is your fourth cousin once removed.
To check a real pair of relatives, add them to the family tree maker and use How related?, or look them up on the cousin chart.
Questions
How many generations back is a fourth cousin?
Five. You both descend from the same third-great-grandparents.
Will a DNA test find my fourth cousins?
Only some of them. Because so little DNA is expected, many fourth cousins share no detectable segment.