He did not work for them before. He worked for company A and got GC from company B and both the companies are owned by the same family (wife (company B) and husband (Company A))
The common family ownership does not mean much unless A and B were part of and controled by the Holding Company which was registered /filed with USCIS and US IRS AND The sponsor for GC.
Your friend really need to look to overall situation....and clearly state the fact situation and compare to what he/she previously stated to USCIS vs Reality.If there are a lot discrepencies, then there is a risk...may , he/she should postopne N-400...until he/she gets facts situation right....frankly, i am not I-485 expert, but the entire I-485 case looks a bit suspect to me. Why company A did not sponsor GC (if he has such a good relationship with owners) ? Was Company B was a used as "shell" company to get GC?
As I stated earlier, creating a document to make to appear things the you prefer (reporting not existent layoff, etc...) is a fraud...In fact, reputable employer will not and shall not engage in that activity.