It might be worth considering that this person lies
– because they have very low self esteem and can’t cope otherwise
– because they are very unhappy about home life, so make up something in desperation as they are upset about or are ashamed of the truth
– have some form of mental illness
All of the above reasons mean tread very carefully. You could do all sorts of very serious damage before you realise fully what the personal consequences might be to the manager.
If you are worried about work issues, make sure you all keep a diary of any work based details, facts or figures that may be questioned later. Note I say work based, not about private issues.
I used to work with someone who claimed a very bizarre private life and had been employed on the understanding he was a barrister (none of our management bothered to check this). He was asked to leave in the end when it became clear he had no qualifications and no clue either. His stories were unintentionally amusing. Our bosses got what they deserved for slack reference take ups. The guy, pretty harmless as a human being, lived in a life that was sad and pretty much a train wreck. Sometimes pity is worth a try…