Mystery Seedling

About three weeks ago I planted two apple seeds. I check them almost daily. But a weekend or two ago I stayed at my In-laws’ for a night and was not around to check on and care for each of my plants. I come back to find there are three little seedlings in the pot. Three? Where did the other one come from? I used bagged potting soil for now as my compost project is not yet set up. Maybe a seed snuck into the potting soil? Maybe it was those pine cones I was handling previous to the apple seedlings? I have no idea. I‘m going to let it grow. We will find out (eventually) what this tiny seedling will be.