You’d get loads of corruption in the recipient selection process and the money would somehow still stay concentrated in the hands of a few. More creative ways for billionaires to not look like billionaires would be developed, leading to more tax evasion, making things worse overall.

Also, what is a “family”? Who gets to receive that money, whose bank account does it go on? Is this worldwide or just families in the country the billionaire lives in? How does one determine where a billionaire “lives”? There are loads of things that would need to be very clearly defined first and would influence the outcome.