Can this be done in a will?

[HoHoHoliday]

I am planning to make a will, and this situation will only come into play if I die before my parent, which is unlikely. I'm in my 40s and in good health, he's in his 70s, but you never know, I could get hit by a bus tomorrow so I want to be prepared.

I have two siblings and a father. A while ago my father announced a new partner, who for various reasons, we all suspect is taking advantage of him. He used to have a will leaving everything to us, his three children, and we now suspect a new will has been made leaving everything to her, he won't discuss it when he's previously been very open. Lots more going on around that situation, but just to set the scene for this question.

I want to make a will myself splitting everything three ways - a third each to my two siblings and a third to my father. But I want to somehow ringfence this third so that it cannot subsequently be left to his new partner. I'd like my father to be able to spend it as he wishes, use it for holidays, or to fund care, etc, if needed, whatever he wants for himself. But if he died before it was all spent then I want the remainder of what I left to him to revert to my siblings, not to his partner.

Can this be done in a will, or would it be that once he inherited the third it would become his to do whatever with?

No, you can’t dictate who he leaves money to in his own will once the money has become his. You can set up a trust, whereby your siblings would ensure the money was used according to rules you set out (such as for your father’s care) but if he had capacity it would likely be a strange and awkward situation to leave them to administer. If your father has his own assets then I’d just leave the money to your siblings, along with your notes wishes that they help take care of your father if he needs it.

Seconding this. You should assume that anything you give your father will go to her. Unless you have reason to think your siblings would desert your father, I would leave all the money to them. Tying the money into a trust would be a huge hassle.