To tell my elderly father that I do have objections to him marrying his partner he met 6 months after my mother died?

DW's parents were both disinherited due to similar circs. There is no need for them to get married. You are entitled to be pissed off, especially if 100s of K are likely to leave the family.

Only on MN are you not to expect any inheritance etc etc.

Man across the street from me took up with a gold digger only six months after his wife of 40+ years died. We all know how this is going to end. She is much younger than him.

How do you KNOW that?
You don't.
But just incase you have those thoughts, make a Will, an individual Will, not a Mirror Will where you leave everything to each other.

If he had a happy long marriage to your mum he might see marriage as more that a certificate but a demonstration of love and commitment. Marriage is more than a certificate to many people at whatever age they are.
Tbh, your posts come across as lacking or wanting to understand why he wants to be married and you are just concerned about your entitlement to an inheritance. Your inheritance can be protected but you will need to have the conversation with your dad and get proper legal advice. It's not an uncommon situation and the legal protection for children of first marriage are well established and tested. So if your dad wants to protect your entitlement, he can do it easy enough.

YANBU. If they marry, and your father passes before her, the Estate that your mother and father accumulated over 50 years will pass to this woman, and her family when she passes.

I don't think are being unreasonable at all.

The problem there was not making a Will in the first place.
To ensure the things you want to go to your own family, then make a Will. It's not difficult, and ensures that specific things - money, property, jewellery are protected. Wills can be updated at any time if circumstances change. Making your own Will is not a slight on who you are married to - first spouse, second spouse - but it is protecting your assessts in the event of your death

You really hope he squanders away the financial remnants of the life he shared with OP’s mother. You actively hope he hurts his children that way. How grim. I bet you think you’re a really good and decent person too for feeling that way don’t you? Fascinating. 🤨

I can understand how the OP feels. It isn't unnatural to later in life hope for a little inheritance. Even if that is in the form of a piece of furniture or picture, a piece of jewellery that belonged to your parent. Something even that may have belonged to grandparents.
With a new wife or husband those things can disappear.
She wants her Dad to be happy.
My own Grandad married twice. And later in life. She inherited being the wife. No Will. Her family basically ignored my dad, and sold everything. He had to go to the auction house to buy some furniture he had loved. If Grandad assumed his wife and her relatives would not behave in that way he was wrong. Very wrong.
So it can be a problem. If the OP dislikes the new wife, she will know it too.
Best to have a frank and open discussion with Dad.

Legally.

Morally, it would behoove this man to carry out his late wife’s wishes.

I really hope he does this! A completely random charity, maybe chosen by the new wife just to really make his grabby children realise how much they upset him when they refused to give their blessing for a last chance of happiness in his old age.

If she left him the money/ assets then they are his. The same would apply if he left it all to a new wife or the OP, once you inherit something it is yours.

The other side of the same coin - what if this lady also has children, and she dies first and everything goes to OPs Dad?...
They are both adults, and making new Wills - who knows, they may have made a Will "in contemplation of marriage" - in which case it will not be revoked.
We only have minimal information about the lives and relationships of the people in this OP.
Dad can get legal advice, and make his decisions based on that, as can the future wife.

Its not your money though. He can leave it all to his girlfriend if he wants. Or the cat's home.

I agree that he is entitled to do what he likes with his own money. But does it follow that the same applies to his late wife’s? Many women leave their estate to their husbands to avoid inheritance tax. But that doesn’t mean they do so thinking their husbands will spend it all and/or effectively disinherit their children later.

As I keep saying, I would be gutted if everything I have worked for went to some random woman’s children rather than (eventually) my DC if I died before my DH.

ETA: inheritance tax aside, it’s also perfectly plausible that OP’s mother trusted her husband completely and never even considered that after 50 years of marriage he would start a new relationship within a few months and there would be a chance of the children not even getting what she put into building the family’s assets. I think that’s why this situation arises so often.

Also, not strictly true about dying intestate.....

He can choose OP to represent him by doing a lasting power of attorney. My son is mine as I know my husband would want to fight to the bitter end regardless of how futile that would and distressing for me. Him marrying has nothing to do with it.

I dont think OP has mentioned if there is already POA in place?
A conversation is definitely needed, but as Dad has capacity - nothing in OPs posts to say he hasn't - he is absolutely entitled to do what he likes with his own money.
Perhaps they are marrying and moving in together to protect money and property? If Dad needs a care home at any point, the house will not be taken into account to pay for the care home if a spouse still lives in the property.

Obviously your inheritance is far more important than your elderly father's happiness.

If he marries but still wants you to inherit that can be dealt with by a solicitor. But ffs, stop being so utterly selfish. I'd be so upset if one of my kids said this to me.

And do discuss the power of attorney topic, it’s not unreasonable for you to be concerned about this. It doesn’t mean you’re right, he may want his new wife to have this control, or they may agree that for the sake of his children it’s better if one of you do.

I understand that, but your post and similar ones miss the point somewhat.

Thus far, he has not taken any of those steps. If he were to marry, especially without sorting out POA, then medical and end of life decisions will be taken by his new wife. On marriage, his will is automatically revoked. If he does not immediately draft one leaving everything to his children and does intestate, everything he and his late wife built up will go the new wife. Who can refuse to give the children anything, even personal effects. Indeed even if he does prepare a will for the children, if the new wife wants to contest it on the basis that she was dependent on him, she may well have a claim.

If all this is what OP’s father is choosing to do, then so be it. But it is mad not to ensure he has taken full legal advice on the ramifications of marrying the new partner.

It is simply wrong to suggest that marriage changes nothing or that he could in any event make those decisions. The latter is irrelevant.

“What a weirdly grabby attitude”

It absolutely is not OP. It is a perfectly normal response. Concerns about your Mum’s legacy are understandable and actually it would be weird not to think about them. Ignore this typically MN virtue signally response 🙄

All the cool kids on this thread who are accusing you of being grabby are probably step children (of elderly wealthy men) who are all in favour of assisted dying. Your father's health and well being means he needs to have someone in his corner to fight for them.

OP, I would ignore those who are disparaging you because of the money side of things, I think if most were in your shoes they would also feel the unfairness of you losing your mum’s money.
Can you get hold of a copy of your mum’s will? This will set out her wishes and may well say that in the event of her out living your father that her estate is to be left to her children. I would then, gently and respectfully remind your father of her wishes and ask if he’s willing to work with a solicitor to protect your late mother’s share should he now wish to remarry.
I appreciate this will not be an easy conversation, but I would have it nonetheless. You can still stress how much you want your father to be happy.

What a weirdly grabby attitude OP. Are you relying on this money for something? Do you have a timescale involved? Both my parents and my in laws have assets of about £1.5m but what they do with that is up to them. It’s not my money. It’s theirs. I hope they blow it all on glam care homes. I’ll make my own way in life without their money thanks because I’m a grown adult. It’s a nice way to live. I’m not building my financial plans purely on parental deaths.

To me this has ALL to do with his partner's and your dad's intention...

And what he hopes will happen after his death....?

He may think... If she looks after me for x years she's entitled to it...

OR if he's intending leaving it to you /your sibs...

Or say... Yes dad, do get married, but please go to solicitor the day after and change your will so your children get inheritance....

(I think on marriage, unless a new will it all goes to the new wife...) .

Selfish?! That's the weirdest comment I have ever seen on Mumsnet. (And there is huge competition!).