It is a quirk of mine that I am almost always a stickler for what particular branch of the armed forces a person is in. (Not to civilians who don't seem to have a clue, and are just trying to be polite.) Fellow members of the armed forces, or authors, I am not so tolerant.
I do realize that for some people the term "Army Brats" may be broadly (Ab)used to refer to kids of any member of the armed forces; in particular those that have (or had) to move from instillation to instillation every year (or at most several years) to year. {Standard tours at a particular location for the US Army are 12 to 18 months. However, reenlistment perks, or a variety of other means can result in staying for 3 years or more. I knew of a superb Mess Sergeant who finagled 15 years of 17 years in the same unit! Win a lot of awards, be able to negotiate your reenlistment, and have multiple Generals who enjoy eating in your Mess Hall and "miracles" can happen! I wonder if he served the rest of his career there...)
The blurb for https://storiesonline.net/s/30347/sister-swap by G. Younger says "Army Brats" but is set at the United States Marine Corps Base of "Twenty-Nine Stumps" (official name Twenty-Nine Palms) and the author seems reasonably familiar with the base. It is Possible although extremely unlikely that a US Army Platoon Sergeant might be assigned to a USMC base... In the story it is mentioned that his ex-wife's father is a General... But then why not nearby Fort Irwin, a US Army base (home to the NTC: National Training Center) an even more desolate Hellhole even further from civilization with fewer amenities.
The US Armed forces now consists of the Military Branches of the US Army, US Air Force, and US Space Force, and the Naval Branches: US Navy, US Marine Corps; the US Coast Guard is also a Naval Branch, although part of Homeland Security during "peacetime"...
I have noticed that US Navy and Marine Corps personnel tend to be more anal-retentive about specifying the difference(s) between Military and Naval.
I have talked with (mostly) military professionals from Canada, the UK, Australia, Germany, France, South Korea, etc. (Canada technically is a "joint force" of Army/Navy/Air Force.) (I mean professionals in terms of long service Regulars, not conscripts or others who only serve for one term, and thus are less likely to know or care about such terms.) Mostly it was Army personnel of dozens of nations, and Marines from the UK or South Korea.
I know there are numbers of people on the forums from various nations, some of whom served in various armed forces, or are at least somewhat knowledgeable about them. There are also quite a few people who are "detail oriented" (aka Anal Retentive) about specifics and details.
I have found that "Army Brats" (or Marine Corps Brats" etc. are often more specific about distinctions between the branches and the military/naval distinction than some (many?) veterans. Some members of my VFW Post only served for 2 years in the armed forces, but one of those years was in Vietnam, or 3 years, but served in a combat theater for Desert Storm, Enduring Freedom, etc. Whereas a Navy Brat has a father and/or mother who probably served for twenty years (give or take a decade) and was likely enthusiastic about their branch (at least enough to reenlist multiple times) in particular for the annual Army vs. Navy football game! A military (or naval) "Brat" is a child/teen whose parent(s) were in the service and lived on or adjacent to a military or naval instillation for a significant amount of their lives before age 18, and usually had to move frequently.
I am not "picking" on G Younger in particular. For all I know at this time the kids are "Army Brats" and their father is for some reason stationed at a USMC base. He is usually quite knowledgeable about details he puts in his stories. I concede that the term "Army Brat" may be used loosely. I am asking other peoples' opinions.
I am asking about specificity in terms of the various branches, as well as military vs. naval services/branches; as well as "Army Brats" vs. "Marine Corps Brats" etc.
In my own stories I am very specific about Branches/Services, etc. (except I may have particular characters "get it wrong" when they are speaking).