It means you reach back into the gene pool.
In my family, I look like my father’s sister. My sister looks like my mother, and we had no idea who my brother looked like. Then we went to a family reunion on my mom’s side. My mom, her brother, my sister, and my cousin looked like 8 other cousins. My brother was a dead ringer for my grandfather’s sister and her son, who we never had met. There were 4 people who resembled me, even though my mother swore I looked nothing like anyone in her family.
I have a neighbor who has bright red hair. Her father has black hair, her mother is a honey blonde, and both of her siblings have dark hair. Her sister had a baby with a man who also has dark hair – their little boy has flaming red hair and looks like my neighbor. It turns out their great-grandmother in their father’s family as a redhead.