I agree, many men in their 60s and 70s find a new partner very quickly. He could choose to leave everything to her and her children.
Often they get married and then chose to “ do nothing “ by not making a will in favour of their late partners children. They just say ( as you are )
” Oh my new wife Betty knows that the house and contents all belonged to my first wife @ColinRobinsonsFart , I’m sure she will do the right thing and leave it all to then when she dies.”
That way they don’t have to feel guilty because they are not actively disinheriting your children and breaking all their promises to you. They are just taking these promises and passing on the duty to fulfil them to Betty.
Meanwhile Betty tells herself that if he wanted the assets to go to the ColinRobinsonFart family, he would have made a will in their favour. Therefore when he dies she has no qualms about keeping everything.
After all, she is the one who looked after him in his old age etc . And then kids are in their 40s, what do they need it for? Whereas she is a widow in her 70s on a pension etc.
In every case I’ve know like this, the second wife ( and her kids ) get all the assets.