Parent router address

We have tried to read parent network address with command atnd. Responce is like this:

4EDB (MY)
0013A200 (DH)
403E19A0 (DL)
RUTER2 (NI)
FFFE (parent network address)
01 (type of device)
00 (status)
C105 (Profile ID)
101E (Manufacturer ID)

Parent network address for the coordinator is always 0.
Parent network address for the router is always FFFE.
Parent network address for the end device is OK.

Question:
Why the parent network address of routers is always FFFE?
Is it possible,somehow, to read parent network address of routers any other way?

Thanks in advance