There are far greater problems, affecting his long term future, in addressing this problem. A check of Census Bureau stats will show that couples who marry or lived together, prior to age 24 have an 85% rate of the relationship breaking down. How old were you and the father when you got together?
Biologically, this is when females reach full mature on the physical, emotional, and hormonal levels. At this point, a woman is fully prepared to have and handle children, as well as a male that is still not fully mature.
Males don’t reach full physical and hormonal maturity until age 30, the age Christ was when he was mature enough to move away from home and make his own decisions.
This is also when they reach their peak emotional maturity, but not to the point of being fully independent. Half of the male emotional health comes from a woman. The biochemical frequency range of the male brain adjusts itself to match that of the female, developing an emotional symbiotic relationship.
Couples who begin cohabiting and/or get marry prior to age 24 can find themselves drawing away from each other as each reaches full maturity. Their whole view of the world, and of each other, changes. This doesn’t happen to all couples, but clearly it is a factor in most relationship breakdowns.
I would not advise encouraging this. None of his military experience is going to change biology. Here's a couple of books for them.
Ten Stupid Things Women Do to Mess up Their Lives
Ten Stupid Things Men Do to Mess Up Their Lives