DLNA through two routers?
That's not really an Android question, but rather network related. But the short answer is:

It should work as long as all the devices described share the same "subnet".

I have a comparable setup here (TV→cable→router→cable→main-router→wireless→tablet), and can use BubbleUPnP fine to stream from my tablet to my PC. All share the same network (192.168.1.*, netmask 255.255.255.0), so UPnP/DLNA finds it's way from end to end. The main router acts as DHCP server for all devices in the network, no other DHCP server concurring.

If however your main router and router2 both use their own subnets, that might get tricky.