It is my personal opinion after researching this story for almost two decades of my life, that Alberto knew his brother left Jean as his sole heir and knew he would only receive a stipend of 100$ a week. I believe Alberto either knew this before Rudy died or in the least on arrival in New York after Rudy's death. When he arrived in New York, it is my belief Alberto called Lou Mahoney in Falcon Lair knowing he had access to the office safe and told him to remove that second page of the will which outlined Jean as sole heir and gave Ullman sweeping authority to continue to run the production company. If Alberto did allow that second page of the will, Paragraph Fourth to surface, then two things would have occurred which did not.
One, Jean as sole heir and being a minor would have had a designated guardian appointed by the court, (usually a lawyer) to protect his interests until he was of age. This is standard procedure. And two, Alberto would have had to come up with some face-saving explanation why his brother did not appoint him as heir and he would have never have had his ability to live such a star lifestyle upon arrival in Hollywood as he did.
With that pesky paper out of the way, Alberto immediately began petitioning huge advances from executor George Ullman based on his “future share” which in reality he never had. I think he always knew he never was Rudy's sole heir. By doing this and receiving a fortune in those advances and then suing Ullman for years, Alberto squandered the estate which was rightfully Jean's and Alberto alone spent the fortune Ullman worked to build up.
In answer to a question posed in the comments here, Alberto benefited financially in every way and then tried with insane audacity to collect it all a second time from Ullman for thirty years. And lest we forget Lou Mahoney witnessed that second page of the will which vanished not so mysteriously, never said a word about its existence in four years while Ullman fought Alberto's false charges and Lou M. has ever since been the sacred cow of the Valentino family...despite his driving away from Falcon Lair with a van full of artifacts.
I make a comparison in saying that if you walk into a room and see a cat licking its paws by a fish bowl spilled and broken on the floor and your fish is gone... it is not rocket science to construct the scenario which took place.
The one other element I would add to this scenario are those final words Rudy whispered to his godfather Frank Mennillo. Mennillo then told those to Alberto on his arrival. I am sure Rudy was not passing on some trivial tidbit knowing he was dying... and in my opinion he could very well have told Frank to tell his brother how the will was in the safe and he left it all to Jean. Alberto would have then acted accordingly...not wanting to be cut out of the monies available and not wanting to publicly admit his brother Rudolph handed him a $100 bill a week. Nada mas.
To me it is a logical scenario to realize based on the timing, the characters involved and what transpired. The fall guy being George Ullman.