Yes, they can be linked. They each must be in the same name and, as you mentioned, the same type of room.
The member holding the arrival day reservation would be the one to call member services to link. He would probably need the reservation number of the second one. A three-way call can be done, but it is not required.
Dining plans and Magical Express (arrival) must be done by the member holding the arrival reservation. The member holding the second reservation would be the one to set up Magical Express departure if needed.
Once the rooms are linked, if you purchase the
DDP, it must be purchased for the entire stay.
I just had 3 different reservations linked and was told that there was no limit as long as the reservations are in the same room and the same type. The only problem I had was trying to make the 180-day + 10 dining reservations. For some reason, the dining system counted each reservation separate. However, I was able to make the dining reservations through Member Services, get the 10-day booking period added.