How do genetics work in Game of Thrones or A Song of Ice and Fire universe? I am asking this because I am confused with hair colors of Jon Snow, Tyrion Lannister, Tommen Baratheon (Lannister), House Stark, Rob Stark etc. Whose genetic is more dominant than others? Is there any genetics dominance chart for GoT?

Also, in GoT usually noble men from the houses marry noble women from other houses. How do female genetics work? Do female characters bring any genetics from their houses or male genetics are always the dominant factor.

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    I don't have the scholarship on ASOAIF to really answer this, but assuming Jon Snow is the child of a male Targaryan and a female Stark, then we know at least one woman contributed to the genetic traits of her child (Jon has Stark hair). We also know the Targaryans practice incest to maintain their hair color, and we know that no recorded child of a Baratheon has anything other than dark hair ("the seed is strong"). All of those facts are consistent with real-world genetics and dominant and recessive traits. Commented Jul 14, 2016 at 19:02
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    Possible duplicate of Heredity in Westeros?
    – Rand al'Thor
    Commented Jul 14, 2016 at 19:28
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    How do genetics work in Game of Thrones? Very well, thank you. What exactly are you confused about? Do you feel like Jon Snow, Tyrion Lannister, Tommen Baratheon, Rob Stark, or anyone else should have different hair colour? Commented Jul 14, 2016 at 23:43
  • @Paul D. Waite I wanted a genetics dominance chart for ASOIAF. Because genetics in that universe confuses me. But after reading the answers I think George Martin replicated real world dominant and recessive genetics. That means it's hard to tell whose child will end up with what hair color, just like real world. Commented Jul 15, 2016 at 0:23
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    I think plotting out an entirely different genetic dominance structure for humans is a bit deeper in the weeds than Martin went. It's pretty safe to assume things match our human traits. Commented Jul 26, 2016 at 13:36

1 Answer 1


Genetics in-universe appear to follow real-world genetics.

All the examples you list follow the dominant trait of their parents:

Jon Snow:

Parents are Lyanna Stark (mother) and Rhaegar Targaryen (father). Lyanna had dark hair (dominant) while Rhaegar had silver/blonde hair (recessive). Jon has dark hair.

Tyrion Lannister:

Parents are Joanna Lannister (mother) and Tywin Lannister (father) (yes, they were cousins). Both parents had blonde hair. Tyrion had blonde hair.

Alternate theory: Parents are Joanna Lannister and Aerys "The Mad King" Targaryen. This is a popular theory because Tyrion's hair color has been described as closer to silver, which is a trait of Targaryens. However, this would not affect the genetics, as both parents would still have the recessive trait.

Tommen Baratheon:

Parents are Cersei Lannister (mother) and Jaime Lannister (father). Tommen is not related to King Robert, despite having the Baratheon name. Both his biological parents have blonde hair. Tommen has blonde hair.

Also, remember from an out-of-universe perspective that actors may not have the exact hair or eye coloring that their characters are described as having in the books.

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    Technically, most of the actors don't even have their natural hair colors (particularly the women) because they're largely all wearing wigs... and even if they're not, dyeing hair in the world of film/TV is extremely common. Similarly, colored contacts for eyes.
    – Catija
    Commented Jul 14, 2016 at 19:41
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    @Catija true. HP failed big time in this as HP ended up having different colored eyes than lily, and all everyone ever told him was he had his mother's eyes
    – Skooba
    Commented Jul 14, 2016 at 20:29
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    i thought she just looked most like a stark where as Sansa didnt look like a stark at all
    – Skooba
    Commented Jul 14, 2016 at 21:16
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    The examples may follow real-world genetics, but there's no real-world genetic basis for the expectation (or, with significant probability, the fact) that dark hair would remain 100% certain in a male line that has married women with other hair colors in multiple generations.
    – Random832
    Commented Jul 14, 2016 at 23:25
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    Random that is correct. It is impossible that all great houses will retain their physical traits for centuries e.g. Baratheons being Raven haired and blue eyed. While playing CK2:Game of thrones mode, this is a great problem. I become greatly annoyed if a Lannister child is not blonde or a Baratheon Child is a blonde (Gasps). So to keep the family traits in, I have to find brides which share similar traits. Life's hard!
    – Aegon
    Commented Jul 15, 2016 at 5:30

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