(one) could be (someone's) (parent/grandparent)(redirected from he could be his grandfather)
(one) could be (someone's) (parent/grandparent)
One is old enough to be someone else's parent or grandparent. Used in reference to two people who are or may become romantic or sexual partners, especially to indicate that the speaker thinks such a pairing would be inappropriate. He's going out with Mary from the legal department? But she could be his mother! I don't feel comfortable with this. I could be your grandfather, for heaven's sake!
See also: could
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.