Q.Why Does My Avocado Plant Have Several Stems?
Started avocado from seed and it has one big stem that is growing and starting to put on leaves but also has what looks like other stem coming out of seed. They look like they may be dying since I potted it.

Certified GKH Gardening Expert
This is a stress related response. It is natural as far as how it is responding. This is a signal that something is off, however. I've noticed that they get a bit sensitive to salts. This means that the soil doesn't need to be overfed, and water should be from a clean source. Water out of the tap is not good for them. However, the biggest thing that I notice is that it looks pretty wet. This will kill off a seedling. If you are noticing signs on the leaves, like yellowing or brown tips or patches, then it might need to dry out a bit between waterings. You can cut off the other tip to focus on the main stem, or you can let them grow out into a bush like shape.
Here is a collection of articles that will help you to care for your tree: