My Dad's sister has traced our genealogy back to Ireland and Germany so she's gone back to the late 1700's and early 1800's. I know paternal Grandma who I adored, she was born back in 1916 which blows me away to think she was born before women could even vote. She died when I was a teenager. Her Father, my great grandpa, was born way back in 1879, 100 years before I would be born. He died long before that, of course.
My Mom's biological father is basically unknown. We know his name, my Grandma was briefly married to him because his choice was to marry her or get charged for statutory rape, but as soon as my Mom and her twin sister were born he was out of the picture. My Grandma never liked to speak of him, she liked to pretend it never happened which can be understood. So sometimes there are forgotten branches because they don't deserve to be remembered.