It was no secret that the Black family had a rather large rift within it. The eldest born of Orion and Walburga Black, Sirius, had always been a difficult child. When the Hogwarts Sorting Hat placed him into Gryffindor their internal struggle grew far faster. This poor child lived in a dark adolescence. His one light being Hogwarts and the freedom it allowed him.
When Christmas break came and he refused to go home. His best friend, James Potter, noticed immediately when the paper for staying at school came around and 'Sirius Black' was scrawled on one of the lines. So James invited him home with him.
Of course Fleamont and Euphemia had heard about their son's new best friend. Not a letter went home without 'Sirius' written in it at least a half dozen times. But they also knew the Blacks. They were distant relations and that was how both sides preferred it. However, James was their only child and he wanted to take care of his new best friend. How could they say no?
When the train arrived the Potter's waited on Platform 9 ¾ with wary anticipation. James's messy hair was spotted through the windows and they tracked it to the door. Their son appeared with a bright smile and another boy in tow. James was swept into a big hug with his parents as Sirius stood back, feeling out of place and awkward, perhaps a bit, or a lot, shy.
As the child Potter stepped back to introduce his friend, they saw he wasn't a Black child. Sure his last name was Black and his parents were Orion and Walburga. Here in front of them stood a shy and awkward pre-teen who was brave enough to join Gryffindor, even if it alienated him further from his closest blood relatives. It took them once glance to see this child shatter their worries. Euphemia swept him up into her arms with a big smile.
It was the first time anyone had hugged him like that. He could feel the warmth and sincerity. Blood rushed to his cheeks and he fought back the dampness that definitely wasn't in the corners of his eyes. His first 'mother's hug'.