These were the posts that summed up my thoughts -
I don’t think it is clear who the money was left to, actually.
The OP says her children were named beneficiaries, but people use legal terms loosely.
The money may have been left to the children and gone automatically into a trust for them as they are under 18.
Or the money may have been left to the OP, with the words “for the education of X and Y”.
If the latter, a lay person might easily say that X and Y were beneficiaries, but they wouldn’t be. OP would be the beneficiary and the wish of the deceased to use it for X and Y wouldn’t be legally binding. In that case, the OP could have split the money with her sister when she had children, of OP believed that her father would have wanted to support all his grandchildren’s educations - but had not expected or anticipated more being born.
OP doesn’t say anything about the creation of a trust or executors, so I wouldn’t rule out the possibility that her children weren’t actually beneficiaries.
And
Everyone is saying that it is legally the children's and she can't do anything... we don't know because she hasn't answered that.
She said they were named in the will, but hadn't talked about the trust being set up and being physically unable to access the money for anything other then her children's education.
Her dad could have left it to them as beneficiaries. Then OP can't because it isn't hers.
Or her dad could have left it all to her, with a simple "for your children" note. That doesn't make them benfeciaies and the money isn't legally theirs.
If it's the former, then OP can do nothing but it is shit for her sister.
If it's the latter, then OP absolutely could have split it. And she knows her dad would want all his grandchildren to benefit, so when her sister fell pregnant she should have discussed with her sister how many children they planned to have so they could come up with a fair split.
I can’t help thinking that this isn’t an OPs-hands-are-tied, money-in-trust situation, because the OP would have just said to her sister that there’s fuck all she (OP) can do about it, that would be that and this thread wouldn’t exist. She’d probably also have mentioned it on this post at some point as so many people have asked about it.
The fact that she hasn’t, and that she’s tried to justify it with all the talk of her sister’s big house and cushy lifestyle makes me think that actually, she could have shared the money, she just didn’t want to.