Siblings of Hyperlexic Children: What Do We Know?

My daughter and I grabbed a few books from the library this morning, and when we arrived home we spread them all out on the floor. Which book should we read first? I prompt her. I assume she will pick one up and bring it to me, plopping down on my lap as she does. But today, she points to a book and says Boo!

Yes. My daughter read her first word today, mere weeks after her second birthday. You would think this was a brag post. But if you are a parent of a hyperlexic child, you know that hyperlexia is both a superability (Grigorenko, Klin, & Volkmar, 2003) and a challenge.

A few months ago at 18 months, my daughter started singing her ABC’s. It was adorable, and my husband and I weren’t very surprised. The ABC song is a fan favorite at our house. To give you an example, we have a Fisher Price album in our car that has three ABC songs on it (Why Fisher Price???), and my hyperlexic son enjoys listening to these three songs on repeat in the car fairly often. With that kind of exposure, we knew she was bound to learn the song early!

But, there’s no way she will be hyperlexic, we have always said to each other. From birth her personality was the exact opposite of my son’s. She exhibited none of the eccentricities my son had. She hit every social milestone like clockwork. Two hyperlexic children…that doesn’t happen. Or does it?

If you have more than one child, you know that siblings rarely have identical personalities. In fact, researchers have found that in terms of personality, siblings share similarities only 20% of the time (NPR). This isn’t really that uncommon, nor is it particularly relative in regard to determining the outcome of hyperlexia siblings. My daughter is spirited and passionate, while my son is calm and contemplative; though opposites, both of these personality types could still showcase signs of hyperlexia.

Personality differences aside, siblings do however tend to fare comparably cognitively. This is the result of nature and nurture. Genes play a signficiant role in our cognitive abilities (Scientific American). And siblings close in age, like my son and daughter, share similar experiences, so it is likely that their IQ scores will be similar (Association for Psychological Science).

So if two children are predispositioned to share so many cognitive similarities, are they destined to share the ability to read early, as well as some of the other characteristics that hyperlexic children have (comprehension issues, social struggles, etc.)?

Several studies show connections between siblings and Autism Spectrum Disorder, specifically the occurrence of Autism in multiple family members (Autism Speaks). Further Autism family research points to these connections in siblings with Autism that also have language-related cognitive disorders and/or social skills deficits, as well (Fombonne, Bolton, Prior, Jordan, & Rutter, 1997). Since there are such strong connections between Hyperlexia and Autism, this could be a useful initial resource to understanding the nature of hyperlexia among siblings.
As I’ve posted before, hyperlexia research is few and far between. What is there does suggest there may be a sibling component similar to that shown in Autism research. For example, one dated study did find a link between hyperlexia and learning disorders in siblings, fathers, and other paternal relatives (Healey and Aram, 1986).

But, is a sibling of a hyperlexic child destined to be hyperlexic, as well? That we don’t yet know. One of the most common answers to hyperlexia questions is the phrase: only time will tell. And until further research is done in this area, that will continue to be the answer.


  1. Hi –
    I have just stumbled upon your site – after stumbling upon Hyperlexia (seems to be almost unknown downunder)
    I was just wondering if you ended up have siblings with hyperlexia or still in the waiting game.
    I have a 6 year old – undiagnosed but the symptoms read like her so very much – and a 3 year old with a very different (and worse) speech delay but same love for numbers and letters – so also in the maybe stage and now I’m ever so curious!
    Loving your site xoxo

    Liked by 1 person

    1. Hi Jodie. To answer your question, my daughter, who is now four, does not have hyperlexia! She is very bright, but does not have the same obsessions with academics that my son (now 6) had/has. We do have a one year old son, as well, and it will be exciting to see how his development progresses. ☺️


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