Unexpected inheritance..do I tell my partner?

Nope, stick it in your savings for you. The money from your grandparent was for you, not him.

although you have been paying half the mortgage and bills - I am guessing you bought a bigger house due to having his kids EOW plus the bills are higher when they are there.
You are not married no reason to tell him about it infact maybe its money you use to leave him because quite frankly if you feel this way about him I am not sure if there is a future for you both in this relationship

If he also has "secret" shares/crypto/savings with which he could pay off the mortgage, and that you don't know the full value of, then I would keep your inheritance in your own savings as an escape fund.
There seems to be some secrecy and mistrust in your relationship with your DP which seems odd. Did he have a previous bad divorce which has made him mistrustful?
Do you have a will in place?

This

Up to you if you tell him. Legally he has no right to any of it though even if you were married. Inheritance is not subject to division in marriage .

Ut his prior children and his crypto investments already demonstrate that he will never merge finances with OP. He will never share with her. He will always prioritize his children and himself over her.

OP you deserve a committed, wholehearted, husband. Get out and find someone good.

Invest it, do NOT use it for the mortgage unless he's prepared to pay the same.

I don't think I could be with someone I couldn't trust enough to tell them I received an inheritance. You don't share your finances, so unless he would somehow be able to still access the money without your permission there shouldn't be a reason why you need to keep it secret unless something is very wrong with your relationship. Is that the kind of relationship you want, where you feel you have to hide things like this?

His meanness has come back to bite him in the arse well and truely 😂

Normally I’d say tell him, but given the disparity in earnings and that he’s made you pay 50/50 even when you were earning far less, plus he has £40K+ in personal savings, I’d say stick it in a separate account. Do you think your relationship will last?

Just saw that you contribute to the cost of his kids holidays - that really is unreasonable

He insists on 50/50 hpuseholf costs splits, but then expects you to pay 50/50 of the costs for his kids, he is exploiting your good nature. You were young when you got together with him, and i think he took advantage of this. You are not equal partners.

Don’t tell him and don’t pay off mortgage

I would not be telling anyone if I received any money.

@jellytiptop I wouldn’t be paying a penny to the mortgage but you would have the cash there to buy him out if you split and if that’s what you wanted .
He's very keen on 50/50 so no doubt he would have idea on how to spend your cash. .
any penny spent on the house wether mortgage or re furb benefits him in a split .

You aren’t married don’t have kids . He doesn’t need to know.

Maybe this will make you stop and think about whether you actulay want the relationship moving forward.
Do you what kids ?
If you do and you don’t feel secure with him then maybe time to get a move on .
You won’t meet the right person while with the wrong perosn.

I would absolutely not tell him about the money. I’m guessing you have had to have a bigger house than you possibly require to accommodate his DC. You pay 50:50 for everything when he comes as a package.

I think he’s done a number on you (and I say this as someone who has been in a similar position) and you would be foolish to give him any more access to your money.

Put the money into an investment and keep quiet. Meanwhile, I’d be looking at this relationship again with fresh eyes. Is it working for you or not?

Defo don’t tell him!

Step aside from your emotions and focus on yourself. As you say your gran worked hard for this money so I’d say to tell yourself that you’re going to put the money aside for a year in a good savings account and take the time to think what to do about your relationship. Your dp sounds like he isn’t bothering. He’s lucky to have you and that you are a great sm. You are young and in a well paid job. You can be single and find a better relationship in the future.

I think you should tell him. It’s not healthy to be keeping secrets like this in a relationship. The fact that you think you need to keep this a secret says the relationship is not great. I think his reaction to your inheritance will be very telling. If he’s happy for you and encourages you to use it for your own financial security then that could really strengthen your relationship. If he starts getting grabby and expecting you to put any of it in the shared pot despite having refused to do this with his own money, then that gives you the very clear information you need to make the decision to end the relationship. I can completely understand why you feel that you want to keep this a secret, but if that’s really what you want to do then you really should be looking to end the relationship now.

Stick it in your own savings or savings bonds, don’t tell him and build up the interest on it. Just pay the mortgage as you have been doing, it doesn’t sound like your relationship is going to last and he’ll have a claim 50/50 in it if you do put it in.

I'd take this as an opportunity to leave him - he's not a supportive partner, you don't trust him, he's mean.

You can force a sale of the house and buy a home for yourself, or buy him out if he'd agree and you can afford it and want to.

You're only 31, you shouldn't have to live like this. You're not responsible for his mental well-being, or for his kids happiness. He has been building up savings when you had far less and were financially suffering, so he's not treating you as a partner.

I'd be putting in my fuck off fund.

All unmarried women need a fuck off fund (or so my friends mother always said. I'd probably extend it to ALL women!) So they can walk away if they need to without worrying about how they'll cope financially.

Put it in your own savings or pension. Do not pay off the mortgage-he has savings if he was interested in doing that.

Don't put it into the house whatever you do and don't let it go into any sort of joint account even briefly. He has kids that stay and yet expects you to pay 50/50. Whilst earning more than you he's been you to subsidise his kids, he doesn't deserve to know. Context means a lot, I'd give the same advice to a lower earning man who'd been expected to subsidise his partners children while she kept everything else in her own name, you either have joint finances or you don't, if you don't share the gains it's not fair to expect your partner to subsidise the costs.