New banana plant.

They grow new shoots from the roots.

I agree, it's a new stalk of your banana plant.

Should I remove it? Re-pot it? Or is it natural for that to pop up? I'm just worried that with it growing in a container they will start to fight for nutrients and then neither one will progress well.

Leave it on for two reasons. The main reason, you need the most stability in the roots for plant support for when the banana fruits. Second, its best to have multiple stalks for more frequent fruiting. When the "first" stalk fruits it will die and automatically generate a "erplacement" rhizome. This will leave you with a staggared age of stalks which will give you more frequent fruitings.

Put it in a bigger pot when there are a couple more if you're concerned about nutrient levels.

When you see them on a plantation you'll often see an old stump with a full sized plant with fruit and between one and four mini's of various sizes all growing in a clump.

Agree with the above advice. They are all part of the same plant.