Whoever they are they sound a nightmare to be around!
It's impossible to 'diagnose' anybody online obviously and that is not what I'm ever trying to do on here. But I strongly think that Personality Disorders are often overlooked when it comes to trying to understand or even change a person's behaviours. (don't even bother!)
The things that you describe make this person a total bully and a shit (to be blunt) but it's worth considering the possibility that constant manipulation of the truth, pathological lying and other consistent behavioural anomalies, might signify a PD.
I am not for one moment saying that PDs (and as has been said already by gettingagrip and me and others, PDs exist on a spectrum from mild to full-blown and also many people with PDs display the characteristics of more than one single Disorder) make such behaviours excusable, only that it can be useful to have a 'label' for such destructive and cruel treatment of another person.
That's because, knowing what you are dealing with means that you can stop continually trying to understand or resolve these behaviours with a PD partner, stop allowing them to mentally screw you over, and instead come to see that you are their victim and most probably need to get out of the relationship or sever all contact with a family member etc.
With Narcissistic PD, the advice is always to run run run run away as fast as possible. Cut all contact and don't look back. N's are not treatable.
But as others have said, other Disorders do seem to respond to some help - therapy/medication. But it's often a very long haul.
Does this help? I could go on for hours about it as I read so much about all this stuff after my exH abandoned me and our baby son taking all our money and going to Thailand. He was a shit alright. But he was a mad nutter of a shit with NPD too (not that he was officially diagnosed but, as I say, reading up a lot about it after he had gone, I realised that he fitted every single criteria and after all, it just wasn't a 'normal' thing to do!).
Seeing this made it easier to cope with eventually, and helped my recovery. I could never have 'fixed' him, and there were many things in his family background and childhood that had made him like he was. It wasn't me. I know also that he has made a major fuck-up of his life. He has lost everything including three lovely children.
But I don't feel any pity for him. And I don't feel guilty anymore (well, only in rare moments when I have a wobble, as it completely traumatised me) for anything I might have done to 'drive him away'.
And I am glad he has gone. His PD made him hell on earth to live with and he will just go on to repeat the NPD pattern of 'idealise, devalue and discard' again and again.