Hilton no longer offers joint accounts so unless you already have one you aren't opening one today.

You can get 4 different HH Amex cards and put any Hilton Honors number on them you wish, maybe all 240K points get deposited in the same account maybe not......my bet is on not.

Since Hilton lets you book reservations and add another person to the reservation who can check in without the person who booked the reservation being present the only way having all the points go into one account would be of any benefit would be if you are booking a 4 night award stay (AXON) or a 5th night free award