Our will is 18 years old

As you don't know what will happen in your children's future divide everything equally. Nobody knows what the future holds and we have seen only too recently how things can come to a halt and crash.
With the share of money your son would receive, it would hopefully be enough to put a down payment on a studio or something bigger because he is saving money while he is living with you. If your other children don't need their part of the inheritance at moment, they can decide that their share will help their children onto the housing ladder when the time comes but that is their decision.
Moreover, who knows that maybe your son falls, as many men have before him, for a gold digger.
Family does not share money, as several friends of mine have found out to their cost.

I don’t agree with giving one child more than another - things can change , one of your daughters might lose their job or become ill, your son might marry a wealthy woman, who knows.

Make a new will. DO NOT rely on your son sharing - that is asking for trouble.

Divide your property as you like, but make sure that your wishes are clearly expressed in your will.

I have 2 children and 2 grandchildren. Both children are doing ok, and my son will get an inheritance from his father my ex, if he has anything to leave. Who has nothing to do with his daughter or grandkids.

So I have split whatever I might have left over 4 ways. Much more use to the younger generation

Leave your assets to your three children in equal measure, it’s the only fair way.

Namsnanny our will is very specific about what happens if any of our children predecease us and also covers other eventualities.
We paid a substantial sum to make sure that the fine details were covered.
We previously had a cheap basic will and realised it wasnt tight enough.

I couldn't leave more to one than the rest ,how awful would your daughters feel if they think because they're doing well you're leaving them out .I'd rather make it a condition of the will the house is sold and the proceeds shared then your son can make his own housing decisions

Marydoll ...Just thinking, if dd's die before ds they don't t get the benefit of mums largess, and it should be documented in the will who becomes the heir in that circumstance.

We had an old will and updated it as circumstances changed and also added power of attorney at the same time make things simpler for our children.

Our children have equal shares, regardless of their income or assets. I wouldn't hurt them, by giving one preference over the other two.

Could you make a provision that your son owns a third and can remain in the house for his lifetime? On his death your other children could then get their share.

You may find it cheaper to write a new will than go to a solicitor to change the one youve got. I used www.tenminutewill.co.uk/
easy to do and easy to understand. As I am estranged from two of my children ( their choice not mine) they arent named in my will. Everything goes to my son.

Absolutely get your will changed, but it might be best to tell your daughters that you are leaving the house to your son. Otherwise your son might have to defend his legacy.
TBH I can’t understand why parents don’t leave their children an equal share each, I think it’s unfair and can be deeply hurtful for the other family members. Anyway , sorry that wasn’t your question, just my personal opinion on the subject, feel free to ignore.

You need to write your wishes down. Don’t rely on people to be magnanimous after you are no longer present! Definitely rewrite your will with a solicitor.