Thanks for your post Rainydaiz. I appreciate what you are saying, however the situation differed in that my ex already had a two bedroomed property when he met his new wife - she did not contribute any savings. They then went on to buy a three bed property together based on their joint income using the profit from the two bed. He has decided to leave her this, plus a pension that he has. An additional factor is that he was only able to get his two bed by receiving money from a property I had, because his name was on the mortgage although actually he did not pay towards it (at the time we were separating and in order to get a mortgage I had needed someone to co-sign it). I wasn't well when this property was sold and thought that legally I had to give him half the profit, but the reality was that he hadn't paid into it.
On top of this, my father also helped him financially in the past at a time when he had a higher income.

So, overall I think that it would be the right thing for him to pass on to our son something - given that his wife could still live very comfortably in a smaller home - especially when our son has very little family support from anywhere else, whereas his wife has an extended family.

However, I realise I can't decide what he does. I've tried to express my concerns to him over our son's feelings at being excluded, but so far he has been defensive. The fact that he has now arranged for his wife's father to stay, without telling the father that he even has a son and preventing our son from returning home, just seems to me to be emotional cruelty on his and his wife's part, although I think there could be some degree of ignorance.