Think of any great romance. Now remove the obstacle. What is left? "Romeo and Juliet" without the feuding families is just two teenagers in Verona for a weekend. "Titanic" without class divisions is just a wealthy girl and a poor boy on a boat.
A classic "Romeo and Juliet" setup where families or groups (like rival gangs, opposing political parties, or warring fantasy kingdoms) make being together a betrayal of one's own people. Think of any great romance