@kavvYourselfAMerryLittleXmas That is a really horrible situation to be in. As you tell us more, it's all getting so much more complicated.
If I can reply to some of your comments:-
He didn’t make a will via solicitors.
Do you mean he just wrote the will himself??????????
That leaves things open to all sorts of problems.
If he wrote the will himself (and it has been properly signed and witnessed), you really do need to find a solicitor to work out just what sort of a mess he has left behind. If he got a will writing service to do it for him then it may or may not be reasonable. Some are very good indeed, others not so much.
But, do just check that it is a valid will. It must be signed by him and also signed by two witnesses. If he did not sign it or there are not two witness signatures then it is not a valid will. In that case, he has died intestate and the Intestacy Rules apply. In this situation, your mum gets the first £322,000 and then shares anything above that amount 50/50 with the children.
This is actually another problem because I have a copy of the will, but not the original. It now transpires that in the last year, DSis was house sitting DMs house during a bipolar episode and did a huge and random declutter and threw out a lot of paperwork.
We now think DSis must have moved or thrown out the original will because they can’t find it. I am at my wits end with the situation and grieving as well, it’s just too much.
...the copy of the will so we know my dad’s wishes, but no actual will right now (I only found this out yesterday)
One small piece of good news, that is not a problem at all. It is not unusual at all for the original of a will to be lost, for whatever reason, but that a copy still exists.
A copy of a signed Will can still be used in an application for Probate. It cannot be a draft or a copy which is unsigned. It must have his signature and also the signatures of the witnesses.
If the original cannot be found despite your best efforts then you can submit a copy for proving in order to get Probate. This is done under the Non-Contentious Probate Rules 1987 (NCPR 1987), Rule 54:
https://www.legislation.gov.uk/uksi/1987/2024/article/54
You must submit an affidavit (this is a statement of what happened which you affirm is true in front of a notary public) explaining why it is a copy rather than the original is being submitted in the application.
The Probate Registry will consider the circumstances surrounding the application, and decide whether or not to issue Probate or make further enquiries.
In this case, exactly what you said about your sister (it may be that your mum might be best placed to write this as it was her home), along with any medical evidence you have that she was bipolar, would likely be sufficient to explain why you only have a copy and not the original.
You say that there is no trust in the will. By this do you mean that there is nothing that says your mum is a "Life Tenant"?
If this is the case then you and your sisters could go to court and get an order for the sale of the house and kick your mum out, if the court agreed with you.
I presume you don't want to do that.
And there isn’t a trust or anything.
In that case, as long as it's a valid will then between the two living sisters and deceased sister's estate you own 50% of the home and your mum owns the other 50%. At the end of the day, it is up to you all how you want to work this out.
If you did decide to sell the house then, strictly speaking, mum is only entitled to 50% of the proceeds. The rest is divided up between the two sisters and the estate of the deceased sister.
However, there is nothing to stop the sisters agreeing to contribute some of their 50% towards mum's new home.
Here are a couple of examples. The current house is worth £400k so that's £200k for mum and £200k for the children.
Mum buys a new house which including all fees etc for the sale and purchase (eg stamp duty etc) comes to £300k.
Now you might decide to share the cost equally with mum. So mum pays £150k and the children also pay £150k. This leaves mum with £50k in the bank and the children with £50k in the bank which is then distributed to the two living sisters and the estate of the deceased sister. In this case, you will all be tenants in common in the new house with mum owning 50% and each sister (or her estate) owning 16.6%
Alternatively, for example, you might think that's too much money and insist that mum pays £200k and you will top it up to cover the full £300k cost.
In this case, mum uses her entire £200k towards the purchase of the house and the children only contribute £100k, this will leave the children with £100k in cash to be distributed to each sister (or her estate).
In this case, again you will all be tenants in common of the new house, but mum will own 66.6% and each sister will own 11.1%.
If there is no trust set up with any sort of rules governing what should happen then it really is just up to you what you want to do with the money. You are quite open to helping your mum buy a new house - or not, as you wish.
Also each sister may have a different opinion. If there is no trust set up in the will then each sister (or your nephew if he is over 18) is free to do whatever they want with the money and are not obliged to contribute any of their share to your mum's new home.