Can non-Diamond check in with Diamond Plus?

[cruz_happy]

I am Diamond Plus sailing with my sister, I think she is Platinum (?)  and sharing the balcony cabin with her on an upcoming  Oasis of the Seas cruise.  Will I be able to have her accompany me through Diamond Plus registration?  (Do they still have that?  My spouse and I travel in Grand Suites and higher; so I'm not sure if the Diamond-Plus get special check-in lines as they did years ago?). On Oasis, do Diamond Plus get early entry into shows, perhaps when the Key people get to go in?  Other thoughts on benefits a Diamond-Plus gets when in a balcony cabin?  (I understand about the drinks on the card, the best perk!).  Trying to decide if Key is worth it since we will be getting the internet package as well .(I'll watch for a good price if it's worth it.) TYIA. 

[Tlbecker1]

No special lines for Diamond+ anymore.  There is a section in the theater reserved  for Diamond +, Pinnacles and  Suites.  You still enter the theater at the same time as everyone else.

[cruiseguy1016]

If you sister is sharing a room with you, she can check in with you.

[Tree_skier]

anyone can check in with anyone.

[GTO-Girl]

Yes she can check in with you but she will not share any of your benefits onboard….

[Chiliburn]

I think there’s only Pinnacle ,the key and suites express, the rest of us are with the great unwashed.