Goodness, what have I started?! Firstly, this thread has gone off on many tangents and I am making no observation on the different opinions and experiences recounted here, but will attempt to justify/clarify my original post. I posted on AIBU because there was, to my mind, the possibility I was being unreasonable - it's very easy to get wrapped up in your own child's welfare and not to see the bigger picture. I was presenting a situation and was entirely prepared to be told I was BU. However, I was not prepared for the hatred and vitriol with which I was told it, and, to my mind, it was entirely uneccessary to call me vile, grasping etc, when I am simply trying to look out for my child. Yes, I did have a 'tizzy' as someone, quite charmingly, put it, because I'd had enough of the completely unjustifiable kicking I was getting from the same little posse of posters again and again. And yes, even though everyone on here is anonymous, the posters were so vitriolic and savage it did feel like a 'personal' attack. So, I stand by my original premise that some posters on here should probably seek help for their issues, rather than venting their anger on MN.
Anyway, if it makes anyone feel better, which I doubt, the house, in itself, is not an issue. In fact, my op was badly thought out (but even so, I still maintain it didn't deserve the response it received), particularly the 'equal share' part. I focused on the house because it is ex's greatest financial asset, and, as ex considers it his own 'asset', rather than his DS's birthright, I guess I have come to see it that way too. Case in point, it was ex who suggested we both sell our properties and buy somewhere new, not the actions of a man trying to preserve a birthright for his son. I don't want DD to gain at the expense of ex's DS, but neither do I want DD to ever feel that she is somehow less valued by her father than her brother. And yes, I did put money into the house, rather a lot of money, but this is not about my money, this is about a little girl who is going to grow up and realise that her Daddy doesn't put her first (sadly, his DS already knows this about his Dad) and I don't want that realisation compounded by a document in a solicitors office. So, thank you to those of you who have suggested ex's DS should inherit his Mother's share of the house and half of his father's, and DD should inherit the other half of her father's half, and all other assets (whatever they may be) should be shared equally. That seems perfectly right and fair for both DCs.
I don't have much now, which is why I am working part time and studying in order to retrain. Hopefully, in the next few years, I'll have a house of my own again to leave DD. I don't disagree with inheritance if you've brought your children up to be independent and not to expect to live on parental handouts for life. Having lived with financial insecurity myself, I will do all I can to pave the way for DD should something happen to me. And, to the blatantly idiotic enquiries as to whether I have written ex's DS into my will, no, of course not, he is not my child. That doesn't mean that I haven't loved him for five years, but that doesn't make him my child, or even my step-child and DD is ex's child.