Old enough to be somebody’s father/mother
Definition 1 of 1
Pro Tip 1/3Age Difference
The phrase highlights a large age gap, implying a generational divide in social, cultural, or life experiences. 
At 52, David was old enough to be her father, making their shared interests quite surprising.
Pro Tip 2/3Not Literal
This phrase is often used figuratively and does not necessarily mean the person is literally of parental age. 
You worry too much about my life decisions — you're not old enough to be my father!
Pro Tip 3/3Cultural Sensitivity
In some cultures, pointing out someone's age directly can be seen as impolite, so use the phrase cautiously. 
In her culture, saying he's old enough to be her father might be taken as an insult.