Hello Dan,
each router can have only one interface in a given IP subnet.
The only way to provide link redundancy would be to use integrated routing and bridging IRB but it may not work well with subinterfaces
bridge 1 protocol ieee
bridge 1 route ip
int f0/0
no ip address
bridge-group 1
int f0/1
no ip address
bridge-group 1
interface BVI1
ip address x.x.x.x 255.255.255.y
! GLBP commands here
note:
only one link will be up and STP 802.1D legacy is runned on the router interfaces (bridge 1 protocol ieee)
the other link will be in STP blocking state.
The router will interact at STP level with switches so ensure that the switches are the primary and secondary root bridge for each vlan.
Some platforms may support the use of bridge-group under a vlan subinterface, you should check this on your devices.
Most of GLBP / HSRP designs use an H schema with a single router link and an horizontal L2 link between LAN switches.
Hope to help
Giuseppe