Author's Note: I don't condone canon!Reggie's parenting choices and actions but I thought an AU where he's a decent father figure in the lives of his kids would do a world of good, hence my contribution.
In the beginning, Sir Reginald Hargreeves planned to train his seven adopted children with a strict regiment that would keep them bound to him. But as the children grew from infancy to their early childhood, he began noticing the difference in their behaviors. Of course, there were times when they made it especially awkward for him such as their request to 'play' with him, other times it could be as simple as giving him a hug. He did not know what caused them to do such things but it oddly warmed his cold exterior.
Sir Reginald knew nothing about raising children, the closest he had to raising one was Pogo, now a loyal servant. So, Sir Reginald went out one day and bought books on parenting and child psychology to get a head start in the children's upbringing. He did not have to enjoy it, but it was crucial for the children to be stable when using their powers during training and future missions. Later, he also created Grace, a house robot to help him raise them.
There were times when his mind returned to Abigail and how he had lost her, a twinge of melancholia would strike every now and again, and it would always circle back to that day when she passed. The only thing he had left of her were the children, it's true that he could not have all of them but seven were already a handful even for an alien. It was then that he promised he would try his best during the children's crucial years for her sake, but he would keep his true identity to himself.
When the children turned six, he gave them cake as well as presents; masks. Even during the children's birthday, he would sit at the head of the table to let the hierarchy of the family be known to the children which was also the reason why he gave them numbers instead of names.
"What are they for?" asked number Five.
"For future use, a year from now, we will begin your training."
"For w-what?" stuttered number Three.
"You will know within a year's time." Sir Reginald replied swiftly not wanting to burden the children at such a young age.
The children put on their masks, some of them not fitting into their faces. Number Seven was especially having a hard time putting hers on but number Five helped her.
"You'll grow into them." Said Reginald.
The children grew quiet, and Sir Reginald wondered what caused this as it was not discussed in the books he'd read about child psychology. Was it his parenting? He kept the question at bay and placed it on the back of his alien brain.
Numbers Seven, and Four rose up from their chairs and walked over to him, placing their arms around him. He had experienced their hugs before but they often made him squirm each time since his coldness had been his default persona for a long time. The other children followed suit, finally melting down his cold exterior.
He sat stiffly, as the children hugged him that is until he enveloped them in his arms.
"Thank you." The children said in unison with big, toothy smiles on their faces.
Sir Reginald sighs as the children let go of their hold on him and he did the same. He had missed that connection after living for such a long time.