My profound thanks both Smithfield and Rose, your replies have helped me a great deal.
I deserve better from MIL but I realise that such people do not change; their own malformed personality traits are too ingrained now. I am only glad she never herself had a girl because she would have been a carbon copy of her.
At least I realise and did long before DH really did (and I think that knowledge is still painful to him so there is denial there also) that his parents were and are inherently dysfunctional.
I can do a modicum of civility with regards to MIL so I will continue to do that. DH bless his heart does not notice!.
Her two sons (the youngest btw I am married to) have been both emotioanlly screwed up by both of them, DH less so but only because he himself had the will to get out of there as soon as he was able and became his own person.
FIL I have recently learnt is narcissistic as well but in a different way to MIL; he latches on to people (even DH says his Dad talks at them) and attends all manner of committees mainly for the adulation (he's been in the local newspaper), cache, money and popularity it brings. It presents a favourable image to the outside world, image is all important. FIL too changed his surname by deed poll as a young man after a row with his Dad (his Dad was part of a very religious organisation/cult) so dysfunction and family problems were present in his life back then.
As I have mentioned before MIL, FIL and BIL would make a good case study for a clinical pysch. However, these people will never be assessed clinically.
I have learnt over the years that the way forward here is to avoid the Dysfunctional Three as much as humanely possible. I would certainly never go around there with my DS without DH these days. Visits there are curtailed as much as possible.
A friend of mine was amazed that DH and I receive two cards; it was only when I actually showed her the two cards that she was incredulous. Even her own mad IL who she cannot abide does not do that!.
Happy Christmas to all on this thread!