Without being able to examine any of those plants, I would suggest that those trunks close together are sprouts from a common base - not separate plants at all.
This condition often occurs where a parent single trunk has died or been removed - and dormant adventitious buds then sprout to regenerate the plant. After storm damage, animal browsing, human harvesting (like coppicing) - you will find this occurring.
There again, you can try planting multiple seedlings/individual plants side by side. They will eventually increase in diameter and grow against their neighbor. Much like codominant trunks, there will be damage/compromised growing conditions where they collide. This won't kill the plants, but will create a weak or less healthy growing condition. "Tangling" of root systems is the least likely ill effect, but proper full basal flaring and equal rooting attachment for physical stability against winds and other physical forces of nature will be less than what it should be if a single trunk was growing without other trunks crowding it.
