To cancel Christmas for 18yr old DS?

Definitely. Put his grandmother first, not him and his girlfriend. He needs to be arrested for this and the locks changed on his grandmother's house.

Does the reason even matter? He stole from a vulnerable elderly lady - simply call the police and let them deal with it. And I would not want him in my home at Christmas he can not be trusted.

Yes I think 100% go to the police. One poster above said a criminal record won’t help but he deserves a criminal record as he is a criminal! He is an adult and made the decision to steal from her.

People are jumping to so many conclusions here. You can spend lots of money without it being drug related.

My dbro did the same thing. He was taking a lot of cocaine

Yes I think it’s a police matter. Let him take real world consequences. I lived with my Nan when I was 18 and I can not imagine doing this. I use to collect her pension in cash in on a Thursday from post office and then go get her shopping for the week and return home. I would have been mortified if it ever crossed her mind I would even take a penny from her. I was so grateful she provided me a home when my life at home was difficult with my Mum and I would never have repaid it by stealing. I loved and respected her and her providing a home enable me to finish my A levels and go off to University for which I am eternally grateful to her. Makes my blood boil what he had done to his grandma.

It goes without saying really that he gets nothing from any of his family for Christmas. He wouldn’t be welcome in my home again anytime soon either, and I’m another one who’d call the police on him. Your poor MIL. It’s bad enough having someone you don’t know steal from you but when it’s a) your relative and b) you’ve done everything you can to help them it’s truly awful.

I hope the stuff he’s stolen and sold is replaceable and wasn’t of any sentimental value like jewellery.

I think Christmas is the least of your problems OP. I would strongly suspect drugs.

I hope to goodness he is now out of his GM's house and has no access to it.
Stealing from a frail elderly ill person multiple times, let alone the fact it's his GM, is about as low as it gets. There's something seriously wrong with his moral compass.

Does his Nan know?
Has it been reported to the police?

As someone with low empathy and poor morals, the only thing he will understand is consequences. Going to the police will also lay a paper trail to make it easier to convict him for future offences and show up on DSB checks to prevent him working with the vulnerable.

Don’t wait until his Nan dies, the police will be less interested then.

When an adult steals from someone vulnerable you call the police, you don't take away Christmas presents. He's not 10.

He sounds troubled- I would want to know the background before jumping to judgement though. Living with his nan at 18 when he has parents isn’t normal and just because he is legally an adult, doesn’t mean he should be treated like one. His brain hasn’t matured yet. What he has done is pretty bad but being abandoned/ostracised by his family at Christmas won’t help. He is still, emotionally, a child.

I really wouldn’t get the police involved as this will massively limit his life chances but someone needs to talk to him. He needs counselling.

Sounds sensible,also mil is a vulnerable adult who needs safeguarding. Measures need to be put in place to keep her safe

Who on earth is telling you that you were being harsh? Absolutely cancel Christmas for him and consider reporting him to the police or tell him that you will do so unless he pays all the money back.

You say in your original post that, sadly, she has not long to live. If the situation changes and she does make sufficient recovery to return home, then Power of Attorney may be appropriate so that your DH can have control of her finances.
in the meantime, as others have suggested, run credit checks and speak to her bank. If it turns out that he has done more than steal from her bank account, then you will have to call the Police a s that fraud. ( on top of theft)
Given that he has sold some of her belongings, I cannot see how he can be allowed back into her home, so securing the house and changing the locks seems appropriate.
He has behaved appallingly especially to a sick woman who gave him shelter and the lack of remorse is worrying. It is not harsh to not give him presents. It is not harsh to make him pay back what he has stolen. It is not harsh to not welcome him in your home this xmas. He is an adult and has to face the consequences of his behaviour.

I can feel your anger and disgust OP.
I know he's your son but you're quite right..no Christmas for him.

Have you secured her house? I would run a credit check etc and ensure he hasn’t taken out loans etc in her name.i would be spending Christmas organising locksmiths, calling banks to suspend her accounts for now and getting him out.

The lack of remorse or explanation is the most concerning aspect. There is not a chance we would be inviting him over. This is very serious and goes well beyond Christmas.

Sounds like a real sociopath to me. Either that or he's got an expensive addiction. How can you steal from your own grandmother? He can't be trusted around her that's for sure do he needs to move out asap.

I agree it sounds like either he has a drug problem or perhaps even a personality disorder. This is very disordered and extremely selfish behaviour either way. Yes I think you should cancel Christmas. Make it clear (led by his father) that you are appalled by his behaviour, he should be ashamed and anything further like this you'll consider police involvement. Make it black and white where you stand.

People who start off doing things like this at a young age will likely escalate, especially if they think they can get away with it. Nip it in the bud as best you can but I'm afraid as others said you might be dealing with the tip of an iceberg.

I don't think you should call the police - a criminal record for him is not going to turn his life around, it's going to make it difficult for him to get a job, and destroy his relationship with his father. Only his grandmother can make the decision to call the police, and if I was her, I wouldn't.

What he did was terrible, and he has to pay the money back, and I would disinvite him for Christmas.

His parents need to talk to him about where the money went, was it drugs, and let him know he needs to turn his life around, and he's been given a chance as police not called.

Police here too. And probably disown.
I hope he's moved out of that house

Is he taking drugs? Several hundred pounds being frittered away on nothing is a stretch.

I would have called the police too, how does he propose that money is replaced?

Disgraceful behaviour

He should be arrested for this

His behaviour is absolutely disgraceful. He's been taking advantage of a vulnerable elderly woman. I would call the police and I wouldn't have him in the house.