To think that MIL's marriage isn't legal?

[User197923462135]

My MIL got married in a hospital whilst her DH was admitted in the Palliative Care Unit. He died 4 days later.
She has since acted appallingly towards his son; refusing to release his fathers ashes so they could spread them, not allowing him to have any of his fathers possessions, etc.
The son has now contested the Will as he's saying that they were together less than two years and he deserves some of what she has been left.
(Apologies if this gets messy and difficult to follow!)
He has then said that when they gave notice of marriage, they put a hotel as their venue and that the notice of marriage was specifically linked to that hotel. He's then saying that considering their wedding was conducted at a different location and different county, that the notice of marriage is nullified and therefore the marriage is not legal.
I think he is correct. When my DH and I went to give our notice, the registrar told us that if we decide to change the venue, we would need to reapply for a marriage license and give notice again.
AIBU to think that the Son is right and should I say anything to MIL or DH?

if there is a valid marriage certificate it is a valid marriage. No harm in asking about the circumstances in which that marriage was granted (special or additional licensing, etc) but I don't expect that your suspicions are correct. Unless you think the wedding certificate is a forgery?
Sorry.

TestingTestingWonTooFree I don't think she married in order to inherit as such. I think she genuinely thinks she's more deserving and entitled to any inheritance than the son.
I also think that in a weird twisted way that she feels if she has all of his possessions, money, trinkets etc. that she still possesses him and that she's trying to be closer to him by pushing out the son....

This reads like the marriage was already planned and notices given.
The man was then given hours to live, and as a couple of people have posted the ceremony was arranged under special circumstances.

I was in much the same situation, we had given our notices in a early April for 1 June.
Late-DH was diagnosed with inoperable cancer in May and hospitalised mid-May.
I kept in contact with the Registrar and they kept asking me if we wanted they to sort an immediate ceremony in the hospital under the special circumstance rules.

As it happens he was stabilised, discharged from hospital and we married on 1 June in the originally planned location.

If the hospice staff supported the marriage then they would have assessed him as having capacity.

Re: dying intestate (i.e. no will, or will is invalid), if you are in the UK - the distribution is as follows:

www.citizensadvice.org.uk/family/death-and-wills/who-can-inherit-if-there-is-no-will-the-rules-of-intestacy/

This CAB advice is very interesting,would just like to warn anyone who is seperated and not divorced ,a friend of my daughters died suddenly, she lived in her own house with her son. when she died her ex moved in and was apparently legally entitled as they were not divorced, her son was told to leave and the husband moved his girlfriend in,
As far as i know the son was contesting it, but not heard what happened
Also not sure if this still applies [or ever did] but was told a first wife could contest a will made by ex husband