Rabbi Yekutiel Meshulam HaCohen Rappa, the 1st Rapoport - What is the evidence of the father of Rabbi Yekutiel Meshulam HaCohen Rappa?

I haven't seen the book myself, but there is a book on the genealogy of the Rappaport family written in 1861 by Eliakim Carmoly, which may provide some clues. Randy Schoenberg, have you seen it? (It's in a few libraries throughout the United States.)

Maybe the proponent of the pedigree from him to Rabbi Yehudah Ben Moshe HaKohen, "Sire Léonṭin" has some info: Shraga F kahana, Rabbi

Sorry for the delay in responding...

The direct connection is not specifically found in a source, rather it is the result of detective work and the connection of certain facts.
It has been a while since I have been involved in this subject, but here is a basic list of the facts:

Fact: Moshe Hakohen, Rav and Rofei 'Rapa') from Mainz, moved to Venice in about 1455.
Fact: Due to his stature, Moshe Hakohen Rapa was exempted from wearing a 'Jew's Badge' in Venice.
Fact: His brother Yehudah Hakohen moved a few years later to Milan.
Fact: With the departure of the brothers, the 'Hakohen' family of Rabbonim in Mainz was ended.
Fact: Moshe had worked with Gutenberg on his printing of the Bible (as had many of the religious leaders of mainz at the time).
Fact: Gutenberg swore all who worked with him to secrecy as to the technology used, until his death.
Fact: Gutenberg died in 1468.
Fact: Yekusiel hakohen Rapa from Venice printed the first sefer, using the Gutenberg process, in 1472.
Fact: Yekusiel's father had moved to Venice from Mainz about 2 decades earlier.

Now, it is theoretically POSSIBLE that there was another 'Rapa' hakohen from Mainz who moved to Venice at that time. However, it is known that Moshe's brother (the only known brother) moved to Milan, not to Venice.
It is also theoretically possible that this other 'brother' worked with Gutenberg and knew his process.

But as a practical matter, with all respect to Sir Occam: it is highly unlikely that there was more than one 'Rapa' hakohen who moved from Mainz to venice at that time, and who was familiar with the Gutenberg process.

I am very comfortable making that connection, and sticking to it.

(apologies for the sloppiness of this reply, did not have time to carefully review for typos etc.)

b'hatzlacha,

S Kahana

Oh, and the fact that Moshe 'Rapa' hakohen's father was named Meshulem Yekusiel?
Makes a lot of sense that Moshe's SON would bear the same name, but I think it highly unlikely that there was a second, UNRELATED Yekusiel rapa in venice in the late 15th century...

Ah, I apologize for misunderstanding.
You are asking about the elder, Moshe ben Eliezer, circa 1350-1415.
I shall dig into my research pile over the next few days and get back to you with what I have.
One thing I can tell you with certainty: it is not from carmoly...

S Kahana