Beckett and Myles Fowl are the younger twin brothers of Artemis Fowl II. In the Time Paradox, their first appearance in a book, they are age two. They were born to Artemis Fowl I and Angeline Fowl after Artemis II departed to Limbo to help save the Demon fairy family with Qwan, No. 1, and Holly Short in The Lost Colony. Artemis first learns of his younger siblings' existence upon his return from Limbo. In the scene, Butler alludes to the fact that Artemis is now the eldest Fowl child. Both are briefly mentioned in The Atlantis Complex and are now four years of age.
Beckett
Beckett Fowl is the younger brother of Artemis and twin brother to Myles Fowl, and has lovely blond curls. He is very childish, has a limited attention span, and is less attentive than Artemis. Unlike his brothers, Beckett comes off as an average toddler who prefers to spend his time finger painting and causing mischief rather than submersing himself in science and business. Although he does not appear to hold the same interests and high IQ as Artemis and Myles, he has proven himself to possess not only an above-average intelligence but an extremely creative streak. One example would be when he successfully managed to dig a bear trap in the family garden, trapped his brother Myles in the hole, and extorted the lock combination to Artemis's lab from his twin in exchange for the ladder. Beckett's IQ does not seem to go as high as Artemis's or Myles's however. It appears that he is more physical and is stronger and faster than both his brothers.
Beckett and Myles enjoy playing together, both agreeing that playing is more fun than listening to Artemis attempt to give them life lessons. He also does not object when Myles calls him 'simple-toon'. Butler once commented it was possible that Beckett would grow up to become Myles' bodyguard.
Beckett has a set of unusual tastes, such as espresso and treacle - especially the two mixed together. Once, Beckett managed to down several spoonfuls of this mixture before it was wrenched from his hand, and didn't sleep for twenty-eight hours. It is still up for debate as to whether or not pocket pets have become another one of his unusual tastes. According to Butler, Artemis (who at the time was beginning to suffer from Atlantis Complex) lost trust in Beckett after the toddler chewed on the leg of his brother's hamster for a bit.
Myles
Myles Fowl is the twin to Beckett Fowl and has the same black hair as Artemis. He was born sometime during the three years Artemis was in Limbo. He owns a jar of mold which he keeps in his bedroom. He likes to call people "simple-toon" (simpleton) and also has a quote, 'speriment table'. This experiment table set up in his room is a sign that, like his older brother, Myles also enjoys advancing his knowledge of the scientific world. His IQ appears to be very high. It is likely he will grow to have the same brains as Artemis. In addition to this, Myles owns a stuffed toy monkey named Professor Primate, which Artemis programmed to say certain phrases such as, "It's alive, it's alive!" and "History will remember this day, Professor Myles." The toy appears later on in The Time Paradox, used to trick Opal Koboi into believing she has finally snatched the coveted lemur Jayjay. It is thrown over the cliffs of the Little Sister when Opal realizes it is instead a stuffed toy.
Myles and Beckett love each other very much. It was stated that they probably love each other more than they love themselves. They are often seen as a duo. Myles seems be the brains while Beckett is the muscle. Currently, they are looked after by Juliet, who seems to have retired being a wrestler to the twin's bodyguard.
It is briefly mentioned in The Atlantis Complex that his brother Artemis (who at the time was beginning to suffer from Atlantis Complex) lost trust in Myles after he contaminated one of his brother's petri dishes when he wanted a sample for his own experiments. Livid, Artemis set up a lock on his lab door, which took Myles three days straight to solve. Butler also mentioned that Myles cost the family several rolls of toilet paper that were used to write down the possibilities. Not long after, he fell victim to a bear trap that Beckett had dug in the family garden and was forced to provide his twin with the code in exchange for a ladder.