(Current house value - ((deposit / house purchase price)*current house value/100)/2 = Your property value
(Your property value/current property)*100 = your property percentage
100-your property percentage= his property percentage.
Then you each will the percentage of the property you own to your own direct dependents.
Worked example:
House value of 300k
Deposit 10%
300,000-30,000=270,000/2=135,000 (your property value)
135,000/300,000*100=45 (your property percentage)
45% of property left to your DC1 and DC2 (22.5% each)
55% of property left to DSC1, DSC2, and DC2 (18.33% each)
DC2 gets the larger share owing to him inheriting from both, but everyone gets a share owing to the fact that whilst his name is on it, you have still been a family and contributing to the mortgage together.
It’s a shared asset whether in his name or not, he needs to put your name on it and stop treating you like you are just a kept woman.