prh47bridge sums up the situation in the post above. However, I'd just like to add a couple of extra points.
"...they still would like to leave some to nieces and nephews"
In that case it does sound as though this will may be appropriate. Your brother and his wife will need to sever the joint tenancy and send a completed form SEV to the Land Registry:
https://www.gov.uk/joint-property-ownership/change-from-joint-tenants-to-tenants-in-common
"...the solicitors firm is a trustee but also as it stands so would my son be"
This is still the big issue that I have with this will and getting this firm involved as a trustee at all. Just why?
Your son sounds more than capable enough to be a trustee. Instead of this company as the other trustee I would suggest that the other spouse is included as well.
So, on DB's will he nominates your son and his wife as trustees. On the wife's will she nominates your son and DB as trustees.
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"...but surely if you can't use your house for care home fees ( even if this works ) you are left with very little choice as to where you end up."
This just shields 50% of the value of the home from care fees. If you are joint tenants then you both own the entire home equally - like a joint bank account.
If you are tenants in common then you each own a separate, distinct, 50% share of the home.
If one person goes into care and their spouse or partner (over the age of 60 or disabled) is still living in the home then the value of the home is disregarded. So it is likely that there would be no fees to pay anyway.
A typical scenario for care home fees might look like this.
If they are joint tenants. Your DB passes away and the entire house is left to his wife. In later later years, his wife then goes into care. Since she owns the house entirely the council can take into account the entire value of the house when deciding on fees (they don't take account of the whole value but a certain percentage). His wife will be liable for fees until her assessed capital falls below the limit.
If they are tenants in common. Your DB passes away and his 50% share of the house is left in trust to his nephews/nieces and his wife is given the right to live their for the rest of her life. She later goes into care but this time the council can only take into account her 50% of the house when deciding on fees. The other 50% is held in trust and protected from being used for fees.
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Also, don't forget that relatively few people actually go into care, especially men.
At the time of the census there were 11 million people in England and Wales aged 65+ (6 million women and 5 million men). According to the ONS there were 280,000 in care homes.
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Although, your DB is slightly younger than this, the figures won't be too different.
According to the ONS, if you live to the age of 65 then your life expectancy at that time is 83.6 for men and 86.1 for women.
What this means is that, if you are still alive at 65 then you have a 50/50 chance of making it to 86.1 as a woman.
For those women aged 80-84 only 4% are in a care home. So 96% of women this age are not in care.
For those women aged 85-89 there are 8.7% in a care home. So more than 91% of women this age are not in care.
The figures do increase from the age of 90. For those 90 or older there are 21% in a care home. But that still means that 79% of women over the age of 90 are not in care.
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The figures for men are even lower.
For men aged 80-84 only 2.4% are in care. So for men, with a life expectancy of 83.6, there are 97.6% who are not in care.
The figure rises to 4.6% for those aged 85-89