ASL
Shanks, an Omega Mother, found himself completely at the mercy of Luffy from the very moment he met his little ray of sunshine, with a lively and cheerful smile, his little anchor of inexhaustible energy. This child quickly became the center of his affection, and Shanks loved him from their first encounter with the same strength he had only ever loved his daughter, Uta. His alpha daughter remained within the Figarland family of celestial dragons. Through life's twists, when Shanks was only a year old, he ended up lost, rescued by the infamous Pirates of Roger. For 15 years, he lived in absolute unrestrained freedom aboard the Oro Jackson. When his biological family found and reclaimed him, Shanks was already 16 years old. Shanks could never get used to the oppression of nobility, resisting with all his might the imposition of the Figarland family. He genuinely tried, but he could never adapt to that kind of life he despised, ultimately fleeing from Mary Geoise when he was only 20. He set sail and began a life of piratery. Over time, he had his Uta, but things happened; in the end, the only thing Shanks could do for the sake of his daughter was to leave her with her family and distance himself from her.
When Makino told him that Luffy was 7 years old, Shanks was quite surprised, as he had thought the child was at most 4 years old. Luffy, mischievous and energetic, made Shanks feel the urge to steal the child, ride him on the Red Force, and run far away with him. However, the insecurity of the New World for a child prevented Shanks from carrying out such an impulse. He, better than anyone, knew the dangers of the New World for someone so young.
However, it only took a second of carelessness on Shanks' part for Luffy to eat the Gomu Gomu no Mi, and another minute of inattention for him to be kidnapped by some lowly bandits, nearly facing death at the hands of a Sea King. Although Shanks could easily deal with the bandits and save his ward, this experience made him realize that if he decided to kidnap this adorable child and take him with him on the Red Force to the New World, something much worse could happen to Luffy.
Shanks had already failed his own biological daughter; he couldn't repeat the same mistake with his anchor. He forced himself to accept that it was his Omega Mother instinct clinging to Luffy due to his youth. However, at the end of the day, Luffy wasn't an Omega Little; he wouldn't remain a child forever. The day would come when he would grow up and no longer fit the Little mold his biology craved so much for his anchor.
Shanks didn't want to follow in the footsteps of that wretch Shirohige. Whitebeard was an Alpha Daddy determined to adopt one orphaned boy after another, trying to fill a void that Shanks knew very well could never be filled. It was the curse weighing on alphas and omegas like them since the day Omega Littles went extinct. So, leaving his hat behind, he also left a piece of his heart with his little anchor the day he departed. With the promise of someday meeting again when his anchor became a great pirate.
-o-o-o-
Sabo knew in a certain way that Luffy and Ace weren't normal kids. Ace was the first one he met, the wild and fiery child; then, a few months later, Luffy came into both of their lives and simply fit in as if he had always been there. But Sabo noticed that there was something different about Luffy and Ace; he just didn't know what it was. Both had a monstrous strength that wasn't normal for such young children. Additionally, they had easy smiles and tended to easily lose control of their emotions, almost like little kids. For Sabo, it was especially amusing when Ace fought to be the older brother. Being close to both brothers made Sabo happy and fiercely protective. There was something entirely unnatural, but Sabo was too young to understand what it was.
When they moved in together to the treehouse after becoming sworn brothers, Sabo began to notice it more clearly. Small details became apparent; Ace and Luffy were particularly messy eaters, and Sabo always patiently smiled as he cleaned their mouths and crumbs from their clothes when they finished. Both brothers resisted bathing, but Sabo always persuaded them to bathe and get dressed. Occasionally, if they were really tired, whether it was Ace or Luffy, they might have accidents in bed. The first time was surprising for Sabo, but he didn't show anything and simply helped both brothers. He noticed that Ace became especially grumpy and prone to fits of rage when he had those accidents, so Sabo started taking care of both brothers by taking them to the bathroom before going to sleep.
In a certain way, Sabo played the role of an older brother, and taking care of Ace and Luffy (even though he was a few months younger than Ace) brought him deep satisfaction. Of course, he would never express this feeling out loud, as Ace and Luffy would surely react with three distinct attacks, insisting they didn't need to be cared for if he mentioned it. However, Sabo knew his role well. He committed himself to taking care of Ace and Luffy forever, even into old age. Unfortunately, Sabo couldn't fulfill his promise. His noble family, from which he hid, would cost him almost his freedom and life, his memories, and most painfully, his brothers.
Ace and Luffy were inconsolable for months when they realized Sabo had left and wouldn't return. Grandpa Garp had to come back and take his beloved grandchildren on a trip for a while to comfort the two boys who continuously sought the blonde with the top hat who wouldn't come back.