Tyrion is a chimera.

[maesternewton]

Tyrion is a Chimera; he is both the son of Aerys and Tywin.
 

What is a human chimera?

Quote

In human beings, a chimera is a person who has two totally different sets of DNA inside their body.

How does a human chimerism come about?

Quote

Usually, just one egg will fuse with just one sperm. But in some cases, two eggs release instead of one. We call this hyperovulation. Thus, two different sperm cells may fuse with the eggs, forming two separate zygotes instead of one. If development proceeds from here, this process can give rise to fraternal twins. Fraternal twins are siblings that look different from one another but are the same age. But sometimes one zygote can absorb the other. The zygote doesn’t know what it’s doing, and it’s not eating its twin, just absorbing its DNA. In the end, only one zygote remains. That zygote now has two sets of DNA, and will grow into a chimera.

Heterochromia, having congenitally different colored eyes, hair, or skin pigmentation—is the only visual phenotypic cue indicative of genetic chimerism, and Tyrion possess two of these in his eye and hair coloring. For example, this genetics study's section on "When to Suspect Chimerism" is fairly clear:

Quote

In singletons, clinical clues include patchy skin pigmentation, as described by Lipsker et al. [2008], whose patient had bicolored skin pigmentation and another patient described by Gerard-Blanluet et al. [2008], who also had unusual pigmentary abnormalities, iris heterochromia and hemihypertrophy.

Chimerism requires the mother to release two eggs within a day of each other. This is precisely how fraternal twins, such as Jaime and Cersei, are created when the eggs do not fuse together. Fraternal twins run in families because double ovulation is heritable, and women who have one set of fraternal twins are more likely to have a second set of fraternal twins than the average woman.

Aerys lusted after Joanna Lannister, he took “liberties” during the bedding when she and Tywin were married, and they may have been involved before either was married - she was at court as one of Rhaella’s companions. The timeline of events presented in AWOIAF makes it possible for her to have been in the same place as Aerys at the time of Tyrion’s conception.

Tyrion is figuratively a chimera:

Tyrion embodies a striking resemblance to the mythical Chimera in a multitude of aspects. A Lannister, and known mainly as a lion, but he’s the goat of the family. Tywin hates him,  goat's notorious inclination towards lustfulness. Moreover, his alliance with the mountain clans mirrors the adaptability of goats to rugged terrains. With an innate vindictive nature, Tyrion retaliates against his kin during his departure from King's Landing, evoking imagery of a serpent-like tail poised to strike back. He’s also described as pretty monstrous in appearance, given his dwarfism, differing eye colors, and his hair color. Notably, Tyrion's affinity for fire becomes evident during the Battle of Blackwater Bay, which intriguingly parallels his fascination with the dragons.

Tyrion has dragon dreams:

Quote

That night Tyrion Lannister dreamed of a battle that turned the hills of Westeros as red as blood. He was in the midst of it, dealing death with an axe as big as he was, fighting side by side with Barristan the Bold and Bittersteel as dragons wheeled across the sky above them. In the dream he had two heads, both noseless. His father led the enemy, so he slew him once again. Then he killed his brother, Jaime, hacking at his face until it was a red ruin, laughing every time he struck a blow. Only when the fight was finished did he realize that his second head was weeping.

GRRM has explicitly and specifically chosen to inform readers that;

1. Tyrion has physical features consistent with chimerism.
2. Joanna was capable of double ovulation necessary for chimerism.
3. Aerys–Tywin–Joanna love triangle likely existed, all of which are necessary but not sufficient for Tyrion to be a heteropaternal chimera.
4. Tyrion is figuratively a chimera.
5. Tyrion has dragon dreams just like Daenerys.

[sweetsunray]

For those interested: this is a well known theory for at least about a decade that has been proposed by numerous people (just a pic from the dozens of threads on reddit, quora and westeros.org):

• reddit (2016) https://www.reddit.com/r/asoiaf/comments/4mo7u9/spoilers_everything_the_imp_has_three_heads/
• here on Westeros.org:

 

[Castellan]

Popular and with a good basis.

[Mithras]

1. Is there any evidence that GRRM knew about chimerism back in early 90s when he conceived Tyrion?

2. How can it be revealed in the story to the characters? By showing them wikipedia entries?

3. Most importantly, what would be the point?

[Castellan]

2 hours ago, Mithras said:

1. Is there any evidence that GRRM knew about chimerism back in early 90s when he conceived Tyrion?

2. How can it be revealed in the story to the characters? By showing them wikipedia entries?

3. Most importantly, what would be the point?

I'm not saying its proven, but among the nut jobby theories around this is one that appeals to me and seems quite plausible.

1. Don't see why he wouldn't know of it. He would surely know the term 'chimera' since its quite a commonly used term for something that turns out to be mythical (as pursuing a chimera) and educated types who study at Northwestern would presumably know it in that sense and the modern scientific term based on it. The term genetic chimera has been in use since 1944 according to wikipedia. The first article describing a chimeric human was published in 1953. I don't think the character of Tyrion needed to have this at its core when he was writing, it seems like an extra layer than could have been woven in during drafting.

2. Why do some people seem to think that the many such details he has built into the series are going to be revealed, incontrovertibly, not only to every final dumb ass reader, but to characters IN THE STORY??? Why would they need to be? For example, if Jon somehow ended up on the Iron Throne it might happen by a process which didn't involve him ever knowing he wasn't his father's son. There could be characters who speculate on it either openly or by allusion. Readers who have inferred his parentage from the story could feel the quiet satisfaction of seeing the appropriateness of his sitting the Throne.

Granted, it is a bit different because revealing that someone is a lost prince is more a tradition in story telling than revealing someone has rather icky origins that don't impact on his standing that much, so it would be most likely that the issue of Jon''s parentage would emerge openly the books, ie a classic reveal.

If Tyrion became a dragon rider, it could emerge in a round about, never finally proven way, because Tyrion himself has stated the necessity of Targ blood. Tyrion himself might come to believe he is Aerys's child, which would free him of kinslaying.

3. Partly, its just a classical reference which in my view describes Tyrion rather well = roar of a lion, nasty stinging tail of a dragon, and ludicrous head of a goat - his playing  he goat side. But as a little garnish its in keeping with a series that starts with intrigue surrounding a book of blood lines that suggest the royal progeny are bastards. The Targs are based on a lot of imagination about magical genetics: violet eyes, prophetic dreams, heat tolerance and hatching dragons. It doesn't seem out of place in this mix.

 

[sweetsunray]

On 5/23/2023 at 9:26 AM, Castellan said:

1. Don't see why he wouldn't know of it. He would surely know the term 'chimera' since its quite a commonly used term for something that turns out to be mythical (as pursuing a chimera) and educated types who study at Northwestern would presumably know it in that sense and the modern scientific term based on it. The term genetic chimera has been in use since 1944 according to wikipedia. The first article describing a chimeric human was published in 1953. I don't think the character of Tyrion needed to have this at its core when he was writing, it seems like an extra layer than could have been woven in during drafting

His use and mention of "brindled" men and creatures is in support of him knowing about chimerism. Brindling is not always caused by being a chimera, but in essence a chimera is always brindled.