How do you prove that a marriage is legal?

[ASW1964]

My cousin died recently and left all his estate to his wife, omitting his adult children. He married a Thai national in Thailand and we are doubting if the marriage is legally valid within the UK due to the lack of paperwork that was undertaken.
How and where do we check if the marriage is valid as we understand that if the paperwork was incomplete, they can still have a marriage ceremony but it wont be valid in the UK and hopefully his children can now inherit? There is a marriage certificate but no affidavits which were legally required.
His wife speaks limited English and is intent on returning to Thailand with all 'her' money.

How long was he married for?

Did he leave her the estate in his will?

Who are the executors of the will? It will be up to them to check whether the marriage is valid before they release the funds.
Thai embassy? Talk to a family law solicitor who will presumably know where to get confirmation.

But if he chose to leave the money to his wife, and he was of sound mind, surely that’s where it should go.

Does it matter if he was married if he named her in his will as his beneficiary? Seems awful not to respect his wishes.

The affidavits were required so that they could get married. They are not required after marriage. If the marriage was registered with the registrar at an Amphur Office it is valid in the UK. The fact there is a certificate suggests it was indeed registered.

Even if the marriage was not valid, that will not necessarily stop her inheriting. If his will clearly identifies her as his sole beneficiary the money is indeed hers.

How long was he married?
Sadly this is a very common occurrence.
His children need to get proper legal advice fast.
Once the wife goes back to Thailand they have no chance.
If he was of sound mind and the will was properly witnessed, there isn't much anyone can do.

Surely whether or not they were legally married really has nothing to do with inheritance if there is a valid will. If he had died intestate it would be critical, but if he made a valid will he could leave all his money to the Church or a charity or a homeless person he met once or his pet dog.

My entirely amateur understanding is that if his children have been entirely disinherited, they may be able to contest the will and win a portion, but it will be expensive and awkward. And whether or not their marriage was valid in the UK he clearly considered this person his wife. She's as entitled as anyone to inherit.

As always prh47 has it, the validity of the marriage is probably irrelevant if she’s clearly defined as the beneficiary in a will which he specifically made, while of sound mind.

If she was going to “accidentally” inherit because he hadn’t remade a will after getting married then that would be a different situation and the marriage validity would matter, but it sounds as if he sat down, thought “Shall I leave anything to my children?” and deliberately decided not to. Under English law the children probably just need to live with that.

Surely if the will states ‘left to my wife’ and he doesn’t have one then what happens then. If she’s named that’s different.

Surely if the will states ‘left to my wife’ and he doesn’t have one then what happens then. If she’s named that’s different.

If it was drawn up by a solicitor or anyone vaguely competent she is no doubt specifically named.

If they have a marriage certificate they would also be judged legally married, as I understand it, even if it's a Thai certificate. If they followed the process to become legally married in Thailand, a UK court would recognise them as married.