Idiom: Old enough to be your mother/father
Example 1:
Jane met a guy who seemed like a perfect match on her favorite internet dating site, so she decided to meet him in person. But when she saw him, he
was much older than the picture he had posted! She said she couldn't date
someone who was old enough to
be her father.
Example 2:
Tina: I heard you're dating someone new?
Jim: Yeah, she's awesome.
Tina: I also heard she's older than you are?
Jim: A bit - she's 36.
Tina: Whoa! She's old enough
to be your mother!
Jim: She's not THAT much older. I'm 25.
Tina: Still, 11 years is a big age difference!
Jim: She makes me happy, so that's all that matters.
Meaning: The expression "old
enough to be (someone's) mother/father" means that another person is
substantially older than the person in question. The expression is used
to point out a considerable age difference in dating situations, even when the
person is not actually technically old enough to be a person's parent.