Hi ,
In our test scenario , a vlan interface is created and 3 ips are added to the Vlan Interface. 3 nexthop ips for a destination network (81.1.1.0/24)are added which are in the same respective subnets of the above Vlan interface ips. We resolved arp for only two next hops. Even though we have 2 valid next hops for the same destination network, sonic doesn't create a NextHopGroup.
The following are the logs .

root@sonic:/home/admin# config vlan add 1007
root@sonic:/home/admin# config vlan member add 1007 Ethernet8
root@sonic:/home/admin# config vlan member add 1007 Ethernet9
root@sonic:/home/admin# config vlan member add 1007 Ethernet10
root@sonic:/home/admin#
root@sonic:/home/admin#
root@sonic:/home/admin# show vlan brief
+-----------+--------------+------------+----------------+-----------------------+
| VLAN ID | IP Address | Ports | Port Tagging | DHCP Helper Address |
+===========+==============+============+================+=======================+
| 1007 | | Ethernet8 | tagged | |
| | | Ethernet9 | tagged | |
| | | Ethernet10 | tagged | |
+-----------+--------------+------------+----------------+-----------------------+
root@sonic:/home/admin#
root@sonic:/home/admin#
root@sonic:/home/admin# config interface ip add Vlan1007 10.1.1.1/24
root@sonic:/home/admin# config interface ip add Vlan1007 20.1.1.1/24
root@sonic:/home/admin# config interface ip add Vlan1007 30.1.1.1/24
root@sonic:/home/admin#
root@sonic:/home/admin#
root@sonic:/home/admin# vtysh

Hello, this is FRRouting (version 7.2-sonic).
Copyright 1996-2005 Kunihiro Ishiguro, et al.

sonic#
sonic#
sonic# conf t
sonic(config)# config interface ip add Vlan1007 10.1.1.1/24
% Unknown command: config interface ip add Vlan1007 10.1.1.1/24
sonic(config)# config interface ip add Vlan1007 20.1.1.1/24
% Unknown command: config interface ip add Vlan1007 20.1.1.1/24
sonic(config)# config interface ip add Vlan1007 30.1.1.1/24
% Unknown command: config interface ip add Vlan1007 30.1.1.1/24
sonic(config)#
sonic(config)#
sonic(config)# ip route 81.1.1.0 255.255.255.0 10.1.1.2
sonic(config)# ip route 81.1.1.0 255.255.255.0 20.1.1.2
sonic(config)# ip route 81.1.1.0 255.255.255.0 30.1.1.2
sonic(config)#
sonic(config)#
sonic(config)# exit
sonic# exit
root@sonic:/home/admin# show ip route
Codes: K - kernel route, C - connected, S - static, R - RIP,
O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP,
F - PBR, f - OpenFabric,
> - selected route, * - FIB route, q - queued route, r - rejected route

S>* 0.0.0.0/0 [200/0] via 10.28.32.1, eth0, 00:03:56
C>* 10.1.1.0/24 is directly connected, Vlan1007, 00:01:58
C>* 10.28.32.0/23 is directly connected, eth0, 00:03:57
C>* 20.1.1.0/24 is directly connected, Vlan1007, 00:01:57
C>* 30.1.1.0/24 is directly connected, Vlan1007, 00:01:55
S>* 81.1.1.0/24 [1/0] via 10.1.1.2, Vlan1007, 00:00:21
via 20.1.1.2, Vlan1007, 00:00:21
via 30.1.1.2, Vlan1007, 00:00:21
root@sonic:/home/admin#
root@sonic:/home/admin#
root@sonic:/home/admin#
root@sonic:/home/admin# tail -n200 -f /var/log/syslog | grep swss
Jan 19 19:36:35.535319 sonic NOTICE swss#orchagent: :- addVlan: Create an empty VLAN Vlan1007 vid:1007
Jan 19 19:36:36.081641 sonic NOTICE swss#orchagent: :- setHostIntfsStripTag: Set SAI_HOSTIF_VLAN_TAG_KEEP to host interface: Ethernet8
Jan 19 19:36:36.081844 sonic NOTICE swss#orchagent: :- addBridgePort: Add bridge port Ethernet8 to default 1Q bridge
Jan 19 19:36:36.084313 sonic NOTICE swss#orchagent: :- addVlanMember: Add member Ethernet8 to VLAN Vlan1007 vid:1007 pid1000000000009
Jan 19 19:36:36.615909 sonic NOTICE swss#orchagent: :- setHostIntfsStripTag: Set SAI_HOSTIF_VLAN_TAG_KEEP to host interface: Ethernet9
Jan 19 19:36:36.616063 sonic NOTICE swss#orchagent: :- addBridgePort: Add bridge port Ethernet9 to default 1Q bridge
Jan 19 19:36:36.616928 sonic NOTICE swss#orchagent: :- addVlanMember: Add member Ethernet9 to VLAN Vlan1007 vid:1007 pid100000000000a
Jan 19 19:36:38.187778 sonic NOTICE swss#orchagent: :- setHostIntfsStripTag: Set SAI_HOSTIF_VLAN_TAG_KEEP to host interface: Ethernet10
Jan 19 19:36:38.187778 sonic NOTICE swss#orchagent: :- addBridgePort: Add bridge port Ethernet10 to default 1Q bridge
Jan 19 19:36:38.188237 sonic NOTICE swss#orchagent: :- addVlanMember: Add member Ethernet10 to VLAN Vlan1007 vid:1007 pid100000000000b
Jan 19 19:37:10.547675 sonic NOTICE swss#orchagent: :- addRouterIntfs: Create router interface Vlan1007 MTU 9100
Jan 19 19:37:10.556585 sonic NOTICE swss#orchagent: :- addIp2MeRoute: Create IP2me route ip:10.1.1.1
Jan 19 19:37:10.556585 sonic NOTICE swss#orchagent: :- addDirectedBroadcast: Add broadcast route for ip:10.1.1.255
Jan 19 19:37:11.151159 sonic NOTICE swss#orchagent: :- addIp2MeRoute: Create IP2me route ip:20.1.1.1
Jan 19 19:37:11.151419 sonic NOTICE swss#orchagent: :- addDirectedBroadcast: Add broadcast route for ip:20.1.1.255
Jan 19 19:37:12.728041 sonic NOTICE swss#orchagent: :- addIp2MeRoute: Create IP2me route ip:30.1.1.1
Jan 19 19:37:12.728750 sonic NOTICE swss#orchagent: :- addDirectedBroadcast: Add broadcast route for ip:30.1.1.255
Jan 19 19:39:02.864777 sonic INFO swss#supervisord 2017-01-19 19:38:59,901 INFO exited: enable_counters (exit status 0; expected)

Jan 19 19:40:04.725942 sonic NOTICE swss#orchagent: :- addNeighbor: Created neighbor 00:00:01:56:fe:07 on Vlan1007
Jan 19 19:40:04.726474 sonic NOTICE swss#orchagent: :- addNextHop: Created next hop 10.1.1.2 on Vlan1007
Jan 19 19:40:06.897371 sonic NOTICE swss#orchagent: :- addNeighbor: Created neighbor 00:00:01:57:aa:d2 on Vlan1007
Jan 19 19:40:06.898138 sonic NOTICE swss#orchagent: :- addNextHop: Created next hop 20.1.1.2 on Vlan1007
root@sonic:/home/admin# show arp
Address MacAddress Iface Vlan
--------- + -------------- +--------- +------
10.1.1.2 00:00:01:56:fe:07 Ethernet8 1007
10.28.32.16 00:19:99:e0:c3:a1 eth0 -
20.1.1.2 00:00:01:57:aa:d2 Ethernet9 1007
Total number of entries 3
root@sonic:/home/admin#
root@sonic:/home/admin# redis-cli -n 1 keys NEXT

1. "ASIC_STATE:SAI_OBJECT_TYPE_NEXT_HOP:oid:0x400000000034c"
2. "ASIC_STATE:SAI_OBJECT_TYPE_NEXT_HOP:oid:0x400000000034d"
   root@sonic:/home/admin#
   root@sonic:/home/admin#
   root@sonic:/home/admin#

From the above swss logs we see that no NextHopGroup is created even though we have two valid
next hops resolved.

Regards
Sambit