I’ve been advised not to do bequests by percentage because it means the value of everything has to be figured. Better to make specific bequests, they say.
But of course you can’t leave more than you have. So I don’t quite understand the question. You’re not obligated to leave anything.
My husband and his brother spent a good chunk of their father’s money taking care of him with home hospice for three years. They felt it was right to use it on him instead of waiting to inherit it.