Jeff Bezos has an ex-wife, a girlfriend, four children and billions of reasons to watch whether U.S. President Joe Biden¡¯s tax overhaul wins congressional approval.

The Amazon.com Inc. founder¡¯s heirs may have to pay more than $36 billion if the president succeeds in closing a loophole that helps the rich transfer their fortunes tax-free at death.

Under current rules, whoever inherits the Amazon shares Bezos bought in 1994 for $10,000, worth $180 billion today, will receive a so-called step-up in basis, wiping out any capital gains tax liability. Biden¡¯s plan would close that loophole and apply the top capital gains tax immediately when assets transfer to wealthy heirs. If the rate increases ¡ª it¡¯s 20% for holdings such as Bezos¡¯s, and Biden has called for boosting it to 39.6% ¡ª the eventual tax bill would too.