Author's Note: I am going to alternate chapters for this fic. One chapter of developmental differences, one chapter of life differences, and then I will alternate from one to the other. So read this, and then keep in mind that next chapter you're going to see me fictionalize what I just laid out.
Don't say I never tried anything experimental and different.
Rae Development 1
Differences.
In one world, a boy forms in a void of darkness - one X, one Y.
And in another world, the slightest shifting of cells happens - one X, one X.
A girl forms in a void of darkness.
This changes everything, you see.
Her parents are James Potter and Lily Evans. She is their first child, due on July 31st. They decide to name her Rae - doe.
So here is the first distinction. In one world, the parents are expecting a boy named Harry. And in the other, they are expecting a girl named Rae.
In one world, Harry grows more quickly during gestation. He becomes larger, heavier, physically sturdier, with a thicker skull and a bigger brain. He becomes a boy in the truest sense of the infant word.
In another world, Rae's body is smaller and more delicate - but it matures faster.
She is better able to handle challenges outside the womb by birth. She is also less vulnerable to various illnesses, cognitive and behavioral problems, and even death during the early prenatal and postnatal period. Her mouth also moves more often in the womb, an important precursor to suckling and swallowing harder.
Rae responds sooner to external stimuli outside her mother's tummy than Harry does - kicking, punching, twisting, and turning in response. She also habituates, or ceases responding, to external stimuli earlier.
Though larger and heavier, Harry is actually more vulnerable at birth - more likely, for example, to have developmental issues.
Rae is delivered by a Healer at home, in the little cottage in the small village of Godric's Hollow. It is early evening, the cozy cottage lit by fireplaces and candles. Her first hours are cozy and soft, filled with love and her birth parents' smiling faces.
As the next days and months pass, she gets used to the faces of Lily and James and she is their sole focus. From her earliest days, she shows strong magic - making toys float across the room from her or making the record player suddenly turn on from across the room.
Her birth parents encourage this.
Rae was smaller and easier to deliver than Harry. She was also tougher in the face of the new world, better to fight off things like infections. She is less fussy as a newborn than Harry, as her nervous system has matured faster - and this will become important later.
On the Halloween after her first birthday, that evening there is a sudden slamming of the door. Then comes chaotic shouting, flashes of light, and her mother's back through the cot. Sobbing, begging, pleading, then a scream, a flash of green light - and nothing.
A darkly cloaked, hooded figure approaches the crib, and the face beneath the hood is chalk white with slits for red eyes and slits for nostrils. Rae begins crying. There is a cry, a flash of green light, a burning pain in her forehead, a great explosion - and then for a while, nothing.
Rae doesn't know it, but she has already become a Horcrux for Voldemort as well as the Chosen One.
She awakes again on a flying motorcycle - held by her godfather Sirius, her new father. More protective of a girl than he would have been of a boy, he took her away himself. In Harry's timeline, Sirius went after Peter Pettigrew and Harry ended up being raised by the Dursleys.
Peter Pettigrew still escapes, but as a known criminal who blew up several of the Ministry officials who cornered him. Remus eventually moves into the house away in the woods where Sirius is raising Rae. Sirius and Remus fall in love.
And so it is that Rae ends up being raised by a gay couple, two fathers.
Rae is more likely to openly express pain as an infant. She has a keener sense of smell, her hearing is keener but she is worse at pinpointing and localizing sounds than Harry, and her eyesight is worse than Harry's.
There is no difference between their motor skills. However, Rae's motor skills are encouraged less than Harry's are - the first of many social lessons asking for Rae to be less physical than Harry.
Rae is more social at an earlier age than Harry - she speaks more words before him, and begins waving, gesturing, and pointing more with her hands earlier than he does. She even begins stringing sentences together earlier. And though as a toddler Harry is more likely to pretend he is reading, or to wreak havoc flying on his toy broomstick - Rae is more likely to imitate gestures such as hugging or rocking a doll.
Rae and Harry both continue accidental magic into their toddler age, but it manifests itself in different ways. Harry's magic responds more often to fits of temper, while Rae's magic is more likely to fix or do something. While Harry's magic is punished, Rae's is encouraged.
Harry is a fussier and more difficult baby, having matured less quickly - here is where this becomes important. Especially being raised by the Dursleys, he has internalized much more by the time he is a toddler, internalized not only abuse but lessons from his parents that he has to control his emotions. And so by toddler age he is less emotionally expressive than Rae, who was a pleasanter baby with a happier home life and thus is more open with the emotions she is experiencing. She is more likely to do things like smile, chatter, make eye contact, and express open interest. She is even more openly empathetic to others' emotions than Harry is, relating to others more instinctively. She is also trained to be more empathetic and social, and to have more charming interactions with others. She is treated as a more beloved and charming baby.
Even accounting for family differences, Rae is still held more than Harry. She is considered softer, prettier, more delicate, weaker, and finer featured. Anger and distress are discouraged in her, while joy and interest are encouraged. Her physicality is not nearly as emphasized. This is particularly pronounced in Sirius, who is more of the traditional father figure and is deeply protective of Rae.
Meanwhile, anger and stoicism is encouraged in Harry, who is not only abused and neglected, treated with violence by his cousin, but pushed in the direction of motor sports and not held nearly as often. In the example of Vernon, he even has a father figure who exhibits a rather explosive temper. Harry is treated more physically and bluntly, and is less required to be empathetic and read subtle nuances.
Rae, meanwhile, is trained almost entirely verbally and in subtle social nuances.
While Harry gets things like balls and hammers in the few toys he does get, Rae gets many more toys and they are things like dolls and hairbrushes. Her room is pink instead of blue and while Harry is more likely to get older-kid baby gifts, when he gets gifts at all, Rae is more likely to get age-appropriate things like rattles and mobiles. And where Harry dislikes both parent figures but prefers the woman, Petunia, Rae is more likely to see each of her fathers as fulfilling a different role.
So while Sirius is more of the protective father figure, Remus is not feminine exactly but the more quiet, gentle, and nurturing figure. Sirius is good for fun and fits of temperamental protectiveness, full of energy, but Remus is a steady and serious presence. Rae as a girl naturally gravitates toward taking more after Remus as her main role model in her earliest years.
And so she begins to emulate Remus in emotional expression, visual attention, and physical mannerisms.
This means that Rae becomes prone to quiet and loving books and reading time, serious and intelligent, gentle, nurturing, and steady. As she needs glasses from a young age, she slowly forms into a serious, nerdy little bookworm type. At the same time, she is prone to startling outbursts of true, innocent joy.
While Rae's village first home did leave an impression, of gentle and easygoing security, it is her nature retreat in the woods growing up with her two fathers that leaves the biggest impression. Rae becomes comfortable in nature, even barefoot and at ease, and learns to love quiet, dark shadowy places, and greenery.
By the time she is a toddler, Rae has a wild mane of long black curls, black rimmed cat's eye glasses, a serious and confident pale little face, almond shaped bright green eyes, and the infamous lightning bolt scar on her forehead. Dumbledore made Sirius and Remus do a blood exchange ritual with infant Rae, to keep the blood wards in place with her new family, and so she does have a trace of the beauty of Remus and Sirius's families inside her - a bit of Black beauty and elegance, and a bit of Lupin handsomeness.
Her wealthy fathers try to dress her as a toddler, resulting in an odd assortment (alongside her wild mane of black hair and cat's-eye glasses) of padded pink jackets, odd kimono style dresses, colorful scarves, little knit caps, lettered blouses with cute sayings, and long patterned animal shirts.
Rae is raised by two men who exhibit basically male gender roles, and so as a tiny girl she takes mainly after the men in her life - adding a bit of a bend to her serious turn of mind. At the same time, she is very loved - very innocent and toddler, squealing suddenly and happy - and she knows it.