Keeper, Denethor married Imrahil's sister, Finduilas. Making him Boromir and Faramir's uncle.
I know a girl who was an aunt before she was born. Her older, old, old sister had a kid before her lil sis was born.
I do wish they would have elaborated his part as well. I think it would have given Gondor an extra standout guy, then just your normal soldier that got bitten, walluped, whapped, beaten, smashed, and ground up into little pieces. I don't understand why Jackson added all these extra characters on Rohan's side (Hama, Gamling, Haleth, Aldor, Grimbold) but leaves Gondor to Faramir, his lil bud Madril, and the Denethor brown noser Irolas.