So... I did a bit of research about Guillaume Martin, and this is what I found:
GM was born in Paris, on a day in June, when the sun shone bright and his parents had just prepared a typical French afternoon tea, with café au lait, some madeleines and fresh pieces of apricot and melon from Cavaillon, a city where his aunt Daphne lived. That same aunt was there on the day that he was born, helping his mother to give birth, because Guillaume was so persistent with getting the birth done, that they had no time to drive to the hospital.
G was born in a small guest room, not used for some time, where his mother had parked her road bike, the one she did not use in the days prior to the birth. So Guillaume was born next to this bike and the first thing he saw was this bike. It's said the first thing he uttered, looking at his father with his big brown baby eyes, was "e-o", which, as everyone knows, is baby-French for vélo, but also quite astonishing for a new-born, who often only know words like "whaaaaaa".
This intellectual superiority as well as an interest in sports continued to show. He did his bac at the Lycée St Thomas d'Aquin de Flers and later took up his studies of philosophy at the university of Nanterre, Paris. He finished those in 2015. He wrote a play, Platon vs. Platoche, and a book Socrate à vélo, which translates to "How I am going to win the Tour". The book became a best-seller on amazon after Thibaut Pinot mentioned it in an interview, saying he would never read this book, not because he thought it would be bad, but because he was a rider who relied on feelings, not on books. Warren Barguil and Julian Alaphilippe supported Pinot's view publicly and thereby marketed the book further.
There are many stories about GM to be told, and I don't want to write a novel here, but one more thing I found interesting is that he owns an albino dwarf rabbit called Spinoza. This rabbit was given to him by his aunt Daphne when he was six month old. So that rabbit must be at least 26 now! That's quite an age for a rabbit. I found a quote of Guillaume saying he talks about racing and philosophy quite a lot with Spinoza, and this often helps him to clear his thoughts. Spinoza apparently had something to do with the switch to Codifis as well, but I don't know which role exactly he played in that as Guillaume is coy in that regard.