Imrahil's
sister Finduilas is the mother of Faramir and Boromir- thus Imrahil is their
uncle. He is also Eowyn's
uncle-in-law (as she married Faramir).
Imrahil's
daughter Lothiriel married Eomer, making Imrahil Eomer's
father-in-law. Faramir is Eomer's
brother-in-law, since he married his sister, Eowyn.
Here's a rough family tree below, including only Denethor, Faramir, Boromir, Imrahil, Lothiriel, Finduilas, Eomer and Eowyn. Oh, and it also contains Imrahil's father, Adrahil
. Don't mind the dots- they're just there to space it out properly.
............................................
Adrahil
......................................._____|_____ _
......................................|........... .......|
..............................
Imrahil.............
Finduilas =
Denethor
..................................|............... ............____|____
..................................|............... ...........|.............|
...........................
Lothiriel =
Eomer*..
Boromir....
Faramir =
Eowyn*
*Denotes that Eomer and Eowyn are brother and sister.