Who says they can't have a fifth one on the way and sometimes it's good to get away on a isolated planet. 
True good to get away. But I have no plans to add any more Shepard children. Four is more than enough, adding another would make it too complicated. Plus Lineage has already started so that's pretty much locked in now XD
Still I thought they wanted as many little ones as they could get.
The stories would become too complicated. Hence 4 girls only.
It's more fun to come up with children for the others.
It's more fun to come up with children for the others.
Well family vacation then.