I want to know if there is an option to have two DHCP servers with one pool. The reason for this unorthodox is, I have two router in remote locations on the same LAN (10.0.0.0) And sometimes, the main router is down, and I cannot reboot it for sometime. But I want to be able to still use the network with the router that is up but not running DHCP and therefore new devices cannot join in. I can't create two lans because one of my routers does not support WAN. Thank you :-)
Yes, you can do this if you do it properly and your devices allow it.
For the DHCP, what I would normally do to avoid problems is use a larger then necessary subnet, such as a /23 when you only need a /24. Then you assign half of the network to one device's scope, and the other half to the second device. This way there is no overlap between the IP addresses managed by the two DHCP servers.
However the trick you haven't mentioned is what happens when the main router goes down but is configured as the default gateway for most devices. Without something like VRRP or HSRP to share an IP address between your two routers, this becomes a challenge.
Not unless you want address overlaps. While everything is connected,
ping's from each server should verify the validity of the address it's handing out, but as soon as the networks are isolated, each server is very likely to be handing out the same address. And the clients using the "remote" DHCP server will likely lose their address (as they'll have to bind to the other server.)
TL;DR; You're asking for a mess.