Not at all. He is in this instance a made up character (I think). Prince Genarro (1 n, 2 r) - our character - has no entry that I can find in any of my usual sources. That said, Prince Gennaro Bourbon-Two Sicilies (note 2 n, 1 r in the spelling of the first name), can refer to two people. The first is the eighth child of King Ferdinand (the King we meet in the story). He dies aged 8 of Smallpox, and for historical reasons would more usually be referred to as Prince Gennaro of Naples and Sicily. The second is Prince Genarro, son of Prince Alfonso, Count of Caserta - who was a grandchild of our King Ferdinand and died in 1944.
I would suggest he is a composite character that has no place in real history, but has been created to fit in with the overall era. Additionally, I think he was a convenient plot device at the time, but there is little evidence he plays a significant part in the story. I would suggest that as the junior midshipman, we will see very little interaction between him and the captain - as indeed we rarely do with the other midshipmen. Regardless, as Chapter 42 saw the ship transfer to Calvert - headed to St Helena - and the only officer to leave was Clifton, I suspect the Prince will be off stage for some time.