Runawaywife - no (according to 7), her Ex and his wife had the house, with a mortgage together, the mortgage got paid off with insurance/endowment when she died. This is why I think it should be a 75/25 split between the kids. IF she owned it outright before the relationship with 7's EX then it should go solely to his son, yes.
Newteacher - why 'at the end of the day' is it his wifes house? They bought it together, paid the mortgage together etc until an endowment paid it off on her death. The Ex has put as much into it as she did.
Silverfrog - it's really sad the elder two have been brought up like this. Perhaphs as they grow up they will realise that what their Mother & GP's are spouting isn't right. To be honest, I think you should go ahead and do your wills the way you think is right, they have no right to know what is in your wills so they wont know until your DH has died - it really can't sour their relationship then and hopefully by then they will see what you have done is fair. If not, they have been looked after financially and now DD1 needs to be looked after the most.
Quattrocentro - why do you say that the EX had not put anything into it - they (seemingly) owned the house together - it was paid off by a mortgage endowment which they presumably had together also.
Ivykaty - I have been saying that for pages now, yet the majority of posters disagree - I don't understand why?
MissCromwell, it's nice to know a few people agree.
VTB - dying intestate is so irresponsible and makes life so difficult for the people left behind doesn't it. I don't understand why people do it tbh, especially people with blended families. It's not difficult and it's not expensive. I think if there had been a will in place it should have allowed the daughter to live in the house for as long as she wished - if/when it was sold a small share to go to the other children - perhaphs 15% each - that's assuming this is the only decent sized asset, if there was other money they could get that straight away and leave the house solely to the 3rd child - the one that actually cared for & about them.