There are currently some special online application links for Hilton credit cards whose terms do not include Amex’s usual once-per-lifetime restriction on the welcome bonus. If you’ve had the card before and want to earn the bonus again, these may be worth considering. So far, there have not been reports of any negative consequences from using these links.
At the moment, Hilton cards still do not appear to have the same-family card restriction. It’s unclear when that might change, so if you want to apply, you may want to act soon. If you’ve never had these cards before, you can just use the regular application links instead.