Reasons, I'm assuming we'er talking about children of schoolage and younger, and contrary to my 'no', there would always be some circumstances for a single parent to fight, but not by going abroad, their children come first, and should be of paramount importance.
I think we have to split the single parents up in seperate groups, male and female.
I apologise if this is going to upset anyone, but its what I believe, depending on circumstances which would have to be defined, it would be okay for the father to go and fight, likewise, in some circumstances he should not.
I believe that only in an extreme emergency should the mother fight, and then, only to protect her children.
She's given birth to to life, and really shouldn't take it.
As to becoming a single parent after enlisting, thats another topic.