I see sweet gums growing in the nooks of pine trees. If I left them, they would end up looking just like your photo. All it take is a seed from one tree landing up against the base of a tree and let it take root. Over time, they will grow together. I have a fruit salad tree that I bought that has 3-4 different trees grafted to one main trunk, manmade so anything man could do, nature might also accomplish