FreeBSD Gateway, Crossover

[APseudoUtopia]

Hello,

I'm trying to setup a small home network, It consists of my FreeBSD
9.0-RC2 box connected to my modem (just a modem, not modem/router) and
two other systems connected directly via ethernet to the freebsd box.
I'm able to connect to the internet with the FreeBSD box. I can get an
IP via DHCP from my ISP. However, I can't seem to figure out how to
setup the gateway routes and the IP addresses for the other system.

I'd like to have the internal network be on 192.168.1.0/24. I have 2x
2-port NICs in the freebsd box.

em0 - Internet - 1.2.3.4
em1 - System1 - 192.168.1.1
em2 - System2 - 192.168.1.2

I'm kindof lost here. I've played with it a bit, trying to set
192.168.1.0/24 on em1 and em2, then setting the specific IP address on
system1 and system2 respectively. I've also tried manually adding
routes from 192.168.1.0/24 to 1.2.3.4 (my external IP) to no avail.
The system1/2 boxes cannot ping the freebsd box, nor vise-versa. That
implies it's not a routing problem, but a problem with the systems
getting a proper IP address.

Anyone have any tips?

Thanks.