This!

It is up to the property. Technically it is only the diamond member and one guest who is registered to same room as the diamond member.

That said, I have mixed experiences with my family staying in a 2nd room and sometimes am allowed breakfast and lounge access and sometimes not.

Hilton Honors Ambassador this would be a nice feature of the program if the benefits could be extended to rooms booked by the diamond member in addition to their own stay at the same time. (to avoid diamond members making bookings for others while not staying themselves). There already was a change to enable earning of points on additional rooms.. This would be in line with that.

Globalist