While the following explanation is a little humorous and “cute”, do not allow that to detract from the phenomenal truth that it carries:
The Holy Brisker Rov (Rabbi Yitzchok Zev Ben Reb Haim Soloveichek OBM) who lived in Jerusalem toward the end of his life, is fondly called by thousands ‘The Rov‘.
He had a muddle-minded, confused nephew who was the head of YU for many years. His name was JB Soloveitchik. He is called by those who respect him “The Rav”.
Do you know why this is? That the Brisker Rov is called the “ROV” (with a Kametz), and JB is called the RAV (with a Patach)? The simple reason is that the followers of JBS mistakenly pronounce a Kametz like a Patach, but for a more profound sense, read on…
The Radak (at the beginning of 2nd Shmuel) tells us that when people tell a lie they use a Patach and when people say the truth they use a Kamatz. (This Radak is very profound and requires a long explanation, but the point is clear and accurate).
Indeed the Brisker Rov was a true ROV (Rabbi) while JB was simply a faker. A lie.
Stay far away from non-authentic Jews, no matter what their last names are.