Writing a Will - how to split estate between DS and step children?

[imsorryiasked]

Currently struggling with being "fair" but also ensuring DS is not disadvantaged.
DH & I have been together for 23 years. We have one DS together who is currently 7. DH also has DD and DS who are in their late 20's. DD is settled, married with 2 children, rents via local authority. DS is single and less settled, lurches from job to job, currently flat sharing a private rental.
So, DH & I own our house, est value £350K+ with less than £100K left on mortgage. Other loans/credit cards would be covered by savings but nothing left over. We have private pensions but not sure what these would pay out if we died before pensionable age.
As DSC are adults and DS is a minor we are thinking that we should just leave everything to DS to ensure that he is provided for, and then review our Wills once he is 21. However this seems really unfair to DSC if we were to die before the review. I'm really struggling with it and can't come up with any reasonable alternatives.
Does anyone have any thoughts or suggestions that I could consider please?

So in total, your joint DS received 4/6 and the other two receive 1/3 each.

This is what's fair. DSCs have the potential to inherit from their DM as well. DS only has you two.

Agree, your 50% goes to your DS and your husband's 50% gets split 3 ways. They are not "all your kids" and they will inherit from their mother and her family whereas your DS only has the two of you.

If you are worried about there not being enough to see your DS through to adulthood, then you need to take out life assurance.

Dh and I have decided on the 50% to each of us, split between our respective dc equally.

He had a ds, I had a dd, and we have a ds.
So our his half split equally between his 2 sons and my half split equally between dd and ds.

Our joint ds ends up with half and the other 2 25% each, but they will also inherit from their other parents.

The best thing is for neither of you to die before your DS reaches adulthood - so no risky sports etc.

Then you can do your 50% to your DS and your DHs 50% split between his three children.

Even when adults each DC should get a third share of their DF's property and DS gets all of his DM's property. That's what's fair - the other 2 have their DM's property to inherit.

Very unfair to DS not to get a fair share from both parents.

Thanks all. Life insurance to ds is a good solution in the event of our deaths before he is an adult (18/21/25?)
Re DS mother - no assets as she unfortunately likes new cars and holidays on finance that she can't afford.
But also DH did not inherit anything from his parents. I, (assuming not used up by nursing home fees etc, or current wills altered), will inherit 50% of my parents house etc, and also from a childless cousin.

It's irrelevant what your DS might inherit vs his siblings - what matters is that their father's estate is split equally.