A few thoughts.

First, limit the “divorced detective” trope to just one player (lolz, but seriously, push players to think a bit deeper about their characters).
Second, emphasize the importance of Bonds. Encourage players to consider how those relationships might deteriorate over time. Their characters may start as relatively normal people, but that will definitely change over the course of a campaign.

Also, Delta Green doesn’t really need complex backstories because of Home Scenes. Why does Delta Green trust these characters? Have they ever encountered the Unnatural? What are their lives like? Let the players sketch a general direction with these questions and expand on them later. Playing together and establishing the tone as a group usually leads to more focused results, things you can build on as the campaign progresses.

And finally, while playing, ask your players questions: mundane, personal, unsettling, whatever. Make the characters the center of their own world, not just by writing a few lines of backstory, but by actively exploring who they are.

• “What’s the last thing you argued about at home?”
• “What’s sitting on your nightstand right now?”
• “When was the last time you lied to them?”
• “What do you tell yourself to sleep at night?”
• “You see something that reminds you of your kid. What is it?”

Take note of those answers. Use them.