It definitely is possible to
play with one other human as you ask. However, the game is not ultimately designed to be played that way. So, there would need to be some workarounds. The procedure for running such a league would not be as convenient as you might hope. In fact, the set up and actual procedures might be downright tricky. I don't know enough because I have never done that. But do know that there is probably more involved than I would want to tackle. I have been playing the game since version 4 and have been in many online leagues, as well as attempting to create my own online league once.
It is definitely possible to be a commissioner and run an online league in which your friend is the only other human player. I think the best way to run an online league is with a server that acts as host for the league. There are services for maybe $20-$50 per month which provide a server and some help in setting up your online league. Running an online league as a commissioner is not a trivial task. It is really quite an undertaking and would probably be overwhelming for someone new to the game who has never played in an online league. My guess is that this is not an option that you are looking for.
My recommendation is that you both join the same online league. There are a multitude of online leagues available that are already set up and running. This is a really good option if you are new to the game or have never been involved in an online league. You could play head to head against your friend within the league while simultaneously playing against other humans who are running the other teams. The real advantage here is that the commissioner is the one who handles all of the headaches and most of the work in getting a league set up. You and your friend would be able to just join and start squaring off. Also, if you join a good friendly league, the other humans would probably be willing to help you get started and answer questions.