Based on my own family, the cousin niece/nephew/uncle/aunt connection can be either tight or loose.
Give credit where credit is due though.
An incomplete listing and article in USA Today tries to put out who in Congress has a "blood buy-in" in the war. Interesting, but not shocking, is that of those that the majority come from Republican families - that in a Congress that is approx. ~51-49%.
From the USA Today article (not a complete listing I am sure) and a San Diego Trib article from 2004 that fills in some gaps; also this and this. Not all have served in Iraq..
Killed in Combat:I think Missouri is holding its own. Notice that they all come from the Mountain West, Mid-West/Plains, and the South with one California in the mix. Total count 10 USMC, 7 Army, 3 Navy (+ 2 at Annapolis). 0 Air Force. 0 Coast Guard.
Baucus-D-MT: nephew (USMC)
Family members serving:
Biden-D-DE: son (Delaware National Guard)
Johnson-D-SD: son (Army)
Musgrave-R-CO: son (Navy)
Wilson-R-SC: 3 sons: (2 SC National Guard, 1 Navy)
Skelton-D-MO: 2 sons (Army and Navy)
Aiken-R-MO: son (USMC) plus another son about to graduate from Annapolis
Webb-D-VA: son (USMC)
Emerson-R-MO: stepdaughter (Army)
Hunter-R-CA: son (USMC)
Ros-Lehtinen-R-FL: stepson (USMC) and daughter-in-law (USMC)
Brownback-R-KS: niece (USMC) and nephew (USMC)
Hulshof-R-MO: brother-in-law (Army)
Bond-R-MO: son (USMC)
McCain-R-AZ: son (USMC) plus another son about to graduate from Annapolis
That explains why the Marines have so much support in Congress .... but don't snark too much. Of note, not only are the Marines considered a "elite" force - but they also have the greatest casualty rates percentage of any service. You may be able to say a lot, but you can't say that those Congressional families who serve do not put their loved ones in harm's way.
BTW, I tried to make this as a complete list as possible. Any service, Active, Reserve or Guard. If I missed something, just send it on with a url to back it up.