LAN question, can I "merge" 2 separate LANs?

My home system now accesses the internet via Hughesnet. I have the
Hughesnet router with an ethernet connection to my ASUS RT-AC66U
router. From there I am CAT5A wired to computers and TVs via wires
from both the ASUS and a 8 port Netgear switch (GS208). I have a few
handheld devices (phones, tablets) that connect wirelessly. Wireless
connectivity is such that there are two separate WiFi in place, from
the Hughesnet router, and from the ASUS router. For now, I'm using the
Hughesnet router only to connect ethernet into the ASUS, because
anything I connect wired (or wirelessly) into the Hughesnet router
doesn't see any device on the other LAN.
The question is, can these two separate LANs be joined so that any
device connected to either LAN sees devices in both LANs?
Another questions is basically do I have this system set up optimally,
or is there a better way to connect?
The reason for thinking about changing things is that I'm running out
of wired connections, using all 4 ports on the ASUS and 8 on the
Netgear switch, while 3 ports on the Hughesnet router are un-used. I
could add a 5-port switch alongside the Netgear switch, but adding it
only gains me a net 3 additional ports since I have to use one port on
the netgear to connect to one port on the 5 port switch. Using the 3
un-used ports on the Hughesnet router would be cleaner.