Jesus had roughly three years when he directly taught his disciples. When he sent them out, he sent them in pairs, two by two. There may be practical or strategic advantage to sending out people together, but there is also spiritual advantage. In pairs, they could encourage each other, steady each other through unfamiliar situations, keep each other grounded. They could develop and deepen friendships. When family relations already existed, Jesus often encouraged those bonds: we see Peter paired with his brother Andrew, and James paired with his brother John. For others, Jesus helped forge new bonds. No one was left alone or excluded from fellowship, and human connections were made as a matter of course. There are no fifth wheels in the church.
Consider that, at times, Jesus told the disciples not to take extra clothing, extra food, or extra money -- but to take a companion. Having a companion was seen as the most necessary preparation for the journey: more necessary than funding, more necessary than food or a change of clothes. There was no material thing needed for equipment. But spiritually, the journey did not start without a companion.
My own journey in faith -- modest though it is -- began that way. I started my journey when a friend invited me to Sunday school, and I was not alone. My own journey started with a companion -- and started because of that companion, who included me.
There are many divisions in our world, many things preventing fellowship. Most of them are needless, pointless divisions. When we follow Christ and Christ alone, we walk together.