My tree splits into two trunks and it looks like it's coming apart where they meet

Two stems of roughly equal size leaving the trunk at the same height, meeting in a narrow V instead of a rounded U. Down in the seam you see a dark, tight line of ingrown bark rather than a raised, wrinkled ridge of wood. Sometimes there's a vertical crack running down from the notch, a bulge of wood swelling out on either side, or a dark wet stain weeping from the notch after rain. Bradford and Callery pear, silver maple, and river birch often show three or four stems all leaving one point.

Within weeks