In Roman times, soldiers were forbidden to marry, on the understandable grounds that single men without wives and children to worry about were likely to be the most effective soldiers (and less likely to desert). Obviously, modern militaries don’t have that kind of policy, because it is unrealistic.
What I’m saying is, it would probably be ideal for all soldiers/sailors etc to be male and single, but it is unrealistic in this day and age to expect them all to fall into this category...