Why after all the years between episode III and episode IV, there are no force sensitive people other than Luke and Leia? Is Force sensitivity genetic? Why are Luke and Leia the only hope if there are so many others in the Galaxy.

If being able to use the force is genetic then shouldn't the Jedi be forced to have kids rather than be banned from it?

If they are the only hope then everyone in the Jedi order must have had force sensitive parents, meaning that their parents must have disobeyed the Jedi order.

Don't you think Yoda would jump out of his strange little hut and try to find some force sensitive aliens or Humans? Wouldn't Obi-wan do the same thing, and seek out everyone who has a potential to be a Jedi?