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Ah yes, I get the points made in the answers. I should have said, we have a house, which we have put as tenants in common. So that at the very least half the value of the property will be protected for the benficiaries, and the value of it is enough that the amount we have already given could be given to the others, even if we have spent all the 'cash' we have. We had already planned to write in the will that the two who have had a share already would have to have that deducted from their 'inheritance' share.
As far as giving money towards a deposit is concerned, yes mortgage companies are very strict about the conditions, and we had to write a letter saying all those things, like it's a gift, not buying a share in the house etc. Both of them went through with no problems.
Thinking it through, maybe the best idea would be to get each of them to open a savings account in their own name, managed online (by us, or as mentioned by their parents), so that we have control over when they have it, and what for. Then effectively it's 'theirs' in the same way that the ones who have put it into a house deposit have had theirs. We do have enough cash to do this now. We only want them to have it for a house deposit while we're alive. After we're gone we don't propose to make conditions, as long as we're not here we won't have to see what they do with it.
It's not easy is it, if you could rely on a bank account not chopping and changing the interest rate, other than natural rises and falls in general rates, but of course they are competing against other banks for your money, so have to make 'offers'.
It's been really nice to visit our first grand child in her new home, and soon to be visiting the second in hers, and know that we have been able to help them.
I would much rather we enjoy what we have with them, than have them wait until we're gone. Both of our parents had this attitude, they didn't own property so had little to leave when they were gone, but we all had many good times together.