Alvin still alive and not Jacques de Aldersberg!?

[Netaxus]

Source: https://witcher-games.fandom.com/wiki/Alvin
"Jacques also mentions that he knows about Geralt from "a source", which could be wordplay hinting at his past."

"In the scene where Alvin tells Geralt that he wants to be a witcher, the player can answer "Don't become a witcher, become a knight" to which Alvin replies "I will be a Witcher-Knight!" suggesting a knight who hunts monsters"

This is basically Ciri.

A source is a person born with innate magical abilities, or an affinity for "the Force", which are rather difficult to control once they have bloomed. Stressful situations usually work as the trigger for the abilities' appearance. Schools of sorcery, like Aretuza and the facility in Ban Ard, were created to help these children cultivate and control their powers, lest the abilities drive them mad.

Among sources, the descendants of Lara Dorren are regarded as even more special.

Source: https://witcher-games.fandom.com/wiki/Source
Source: https://witcher-games.fandom.com/wiki/Elder_blood

Alivn is not mentioned and he is a man, all others were women.
Alivin is potentially stronger as Ciri as her powers manifest in later age in opposite to him.

Spoiler: Text

If Geralt tells Alvin, "Your visions are a gift, not a curse. It's up to you to use them for good," then the conversation in the Epilogue appears as follows:

Jacques: Only a grand plan pursued without hesitation could save humanity from what I saw in my visions.Geralt: You trust your daydreams that much?Jacques: I never asked for these visions, this gift.Geralt: But you chose how to use it.Jacques: Many times you insisted special gifts should be used for just causes. I chose the most just of causes — saving millions of lives.

-

If Geralt tells Alvin, "Destiny isn't everything. We are masters of our own fate," then the conversation in the Epilogue appears as follows:

Jacques: Only a grand plan pursued without hesitation could save humanity from what I saw in my visions.Geralt: You trust your daydreams that much?Jacques: Many of the gifted foresaw the White Frost. Global cooling is this world's destiny.Geralt: Why fight it then?Jacques: You always believed man makes his own destiny. I seek to change all humanity's fate.

-

If Geralt tells Alvin, "Keep your gift a secret. The lives of the gifted are rarely easy," then the conversation in the Epilogue appears as follows:

Jacques: Only a grand plan pursued without hesitation could save humanity from what I saw in my visions.Geralt: You trust your daydreams that much?Jacques: You think this burden easy to bear? Like you, I tried to hide my otherness. To use my powers to redeem my sin.Geralt: What sin?Jacques: The worst of all. My otherness. So I acted for the common good.

Witcher,

In the ocean of possibility, some events are more likely, and some less. It is not easy to fish out the first, not even when one's intellect stretches through all time and space.

I left his letter for you in the hope that, despite all odds, you will come across it one day, for I must warn you. Mankind is threatened. The prophesied destruction by the White Frost is not just the babbling of some mad she-elf. Perhaps I will have the opportunity to convince you of this in person. If not, I must rely on this letter, which you will read many years from now, at a time when you know more that you did when we first met.

Know that nothing will save the world except preparing its entire population for this catastrophe. The old tales say a Child of the Elder Blood can stave off the danger, but I tried and failed. Ever since I have been haunted by a hideous vision, a crowned wraith. The specter of my failure.

I was the chosen one, and the chosen one failed. You and your brotherhood are our only hope. When the time of the wolf's blizzard comes, men shall perish and only the ubermen will survive. Your duty is to give the world ubermen.

Whatever you think of me, do not fail as I have failed.

– A

Source
Quest: Message from an Old Friend

The problem with this statement is, if he is dead and were Jacques de Aldersberg, he wouldn't talk or didn't understand and he wouldn't see a reason to preserve or wish that the Witcher should bring the over-human, as he forcefully destroyed the option himself, took it form them, at the moment he could write this, he was already dead.

This allows two conclusions, he isn't de Aldersberg or he just is much much more powerful then Ciri and can traverse different timelines. If we observe Ciri we see a clear fighting skill form alternation of spacial teleportation, this weren't by de Aldersberg.

After Geralt defeats de Aldersberg in the epilogue near the end of the quest "Icy Reflections," the King of the Wild Hunt appears. The ghost reveals that Geralt knows de Aldersberg's soul by another name – presumably Alvin.

The soul could be named Ciri!?

If we would use the Netflix conditions of the elder blood, we would know that he was Edler Blood, but this is not mentioned in the books of the Trial of the Grasses.
Otherly could this letter show that he was cooperating with Jacques de Aldersberg and understand this, possible they know each other. Could be his adopted "son" and they share the same amulet or he gave it to him to protect him form his visions. Alvin was young and helpless.
From the source (why calling it source if you can admit it, which problem does it cause. That Jacques de Aldersberg doesn't know if Alvin comes after or before his encounter) his "adopted" son Alvin, one who understood what he felt and helped him in this time. Logically as if Alvin was interested into the Wichter he would search for him, but he can't because he would destroy his destiny origin. Jacques de Aldersberg gave him possibly the first comfort in his experiences with the visions. If not he would have been dragged to Aretuza in the northern Kingdoms, which obviously didn't happen. If he was special Triss would have known him in past.

The letter logical determination says clearly that Alvin is alive somehow!