From: Florida, USA (formerly Chicago)
I would suggest reaching out and perhaps calling a truce on those routes that you already share.
If he is agreeable to that, then live with the truce/sharing the route, and look elsewhere for empty routes.
It is early in the game. You can go anywhere in the globe. I have had 2 routes where someone spammed onto my route. One went over demand, and i simply undercut fares. On the other I added enough flights to max out the route demand, and moved onto the next route.
As 2ndACR mentioned, this early in the game, there are good empty routes everywhere. Take what you can, establish routes, then move onto the next one.
Flying an uncontested route will generate maximum income (thus allowing further growth and expansion).
Contesting with another for a route will mean reduced income, and impede the rate of growth for your airline.
Do the math.
To me, the course of action is obvious.