Can you help me find resources to understand the military match? I am mil-to-mil and my primary concern with USUHS is that I'll match with a specialty/base assignment that sends me far away from my family.
So Matthew9Tthirtyfive beat me to it, but yes - JSGME is the office responsible for coordinating the military equivalent of the civilian residency match process. Each service does it a little bit different, it's not exactly transparent, but from what they tell us it's a combination of looking at our pre-clerkship pass/fail scores and clerkship grades, an arbitrary number of "points" awarded for things like honors/leadership positions/research, and a bunch of residency program directors from each service passing the applications of MS-4s across a big table in a dark room with one lightbulb.
One thing is for sure though, you will get PCS (permanent change of station) orders wherever you get matched to wherever that residency is. With those PCS orders will come the means to transport you and your entire family with you. From my understanding, SOME residencies have optional research or travel months that COULD take you away from your base for some amount of time, but none that I'm aware of would keep you away from your family any more than the physicians in civilian residencies would. We've been told multiple times that residents will NOT be deployed before completing residency, with the exception of folks in GMOs who technically have completed an intern year and can practice unsupervised as a full physician.
That being said, there will be a few weeks every few years that you will probably be separated from your family (Bushmaster Exercise in years 1 & 4, your initial direct commissioning course - unless you are currently an active duty officer, and clerkships - though many students with families often bring their families along or opt to stay in the local area, except for air force med students, who I believe will have to do at least a few clerkships away from the NCR during med school).
Overall, military residencies are in places with large military treatment facilities and large populations of active duty folks to keep them busy enough to support their programs (think Oahu, DC, San Antonio, San Diego, & Seattle areas, not Montana). Almost all of these have suburbs that are great to raise families nearby, and some even have on-base housing if you really want your kids raised in a safe, tight-knit, military community (ex. where I grew up).
TL,DR; I don't have kids yet, but I have enough classmates with young kids who would share similar concerns if it were an issue - and I haven't heard of it from any of them yet. Residency PCS locations tend to be nice and fam-friendly.