I was in the reserves so never actually got BAH, but I remember two things. When I graduated from boot camp(Navy) at least 3 or 4 guys had their wives come to graduation. One of whom already had 3 kids. It was otherworldy to me.
My step-mothers first husband was a career marine. He got out as an E-9. What she told me was that at least early on the marine corps didn’t permit you to get married until you were at least an E-5. I wonder when that changed?