This thesis investigates the derivation of multidominant structures via Merge and the idea thata syntactic node can have multiple associated feature sets. The empirical focus is case syncretism in ATB movement. I examine the behavior of unmarked case and case whose assignment depends on elements external to the conjunction site. Drawing on data from German, Icelandic, and Hindi-Urdu, I show that these two kinds of case behave the same way as other kinds of case with respect to case syncretism under ATB movement, which is unexpected under existing analyses of ATB via multidominance. I argue that in order to adopt Citko (2005) and subsequent work’s analysis of ATB movement as involving shared structure, a different derivational pathway must be adopted, one which does not involve Parallel Merge. I propose a derivational pathway that I call Late Unify, wherein shared structure results when two syntactic objects with elements in common are merged.