Can I splice my 100 ft long ethernet cable and connect two other ethernet cables?
I would suggest getting another 100 ft cable, or a wireless XBOX receiver. Or an inexpensive hub/switch and two shorter ethernet cables. Or maybe you can set the laptop to use wireless and use the exisiting 100 ft cable for the XBOX. Splitting one cable into two probably won’t work without proper software. How would each device know what data to expect? How would the router know which device is sending data?