Luckily I’ll never be in this position but instinct tells me all children should form an equal part of the family and inherit equal amounts regardless of biology. I can’t see uneven splits causing anything but discord and resentment
My kids are still young. Stepdc are grown up.
If dh and i die, my kids are orphans, with no income or support. Leaving my house to them means their guardian will have funds to buy a larger house themselves to accommodate 2 more kids, money for school uniform, university etc.
Step dc will have lost their dad, and will be devastated, but do not need the financial support in the same way. They also will still have a surviving parent to support them financially.
For the same reason if I die my house and asset share go to dc, not dh. Although i trust dh, if he dies intestate or loses capacity it is not impossible he may die and leave everything to his kids, or an equal share, leaving our young dc having to sell their house and leaving them little to survive on.
When all the children are adults i may rethink. But logically, i see an uneven split as fair- our dc will get my assets plus 50% of their dads, step dc will get their mums assets plus 50% of their dads.
An even split means my share of the assets also get distributed to stepdc- so of the 3 adults involved (me, mum, dad) stepdc will get 75% each, our kids get 25%. Still not an even split.
Plus taking into account that anything they inherit from mum, the house, savings etc, was originally owned 50% by dh anyway. He left all his assets in that marriage, and hasn’t been able to build up that level of assets again.