The Rosh Yeshiva of Volozhin – the Netziv OBM – had two sons.
One’s name was Haim. He knew the Nitziv his whole adult life. He was around 70 years old when the Nitziv passed away. Furthermore, he served with his father and nephew, the Famous Reb Haim Brisker OBM, in running the Yeshiva in Volozhin. He was a great, authentic Tzadik.
But the Netziv had another son. He was only 14 when the Netziv passed away. His name was Meir Berlin. He later changed his last name to Bar-Ilan (which literally translates to “the son of a tree”!). He was close to the infamous Mizrachi movement. He was very different from his brother, Reb Haim.
No genius is required to grasp which one “knew” his father more accurately. One knew his father his entire adult life, the other was a small boy when his father passed on.
This is why they look and behaved so differently.
The Holy Hafetz Haim OBM once said to Meir Bar-Ilan “Du Has Nit KeKent Dem Taten!” – “You did not know your father”. How true…