Luke was the middle child of the family. Unlike most middle children who whine about their position, he was actually quite content with his role. Being the middle child meant that he gained freedom. He wasn't as closely watched as the baby of the family, his little sister Casey. And he didn't look as suspicious when placed next to his elder brother, Mike. Overall, he was generally left alone, trusted.
Along with being the middle child, another thing that went against him was his personality. Luke wasn't a very sporty person. He went for jogs occasionally, but that was the extent of his athleticism. It wasn't that he was bad at it, he just didn't find any interest in it. On the other hand, his father and elder brother were very athletic. His brother played a multitude of sports, while his dad was a coach for high school football. This wouldn't seem to be a problem, as both his mom and his little sister also weren't very athletic, but then, they also had something in common. Hobbies. They both liked to knit, bake, and cook. Three things Luke absolutely despised. These things, he was bad at. He preferred to sit on his bed and enjoy a good book. That or spend some time sketching in his sketchbook. And so, he didn't quite fit in in his family. They still tried to hang out with him, but most of the things he liked to do were solo activities, so very rarely would he come up with something to do with his family.
This, again, he was quite fine with. He didn't mind being alone, he actually liked it. Luke didn't find company to be entertaining or pleasant, he chose solitude over that. He knew his family loved him, and so he was ok no matter what.
Luke was quite a curious kid, he liked to learn things, and as a result was very studious. He was proud of his grades, and his family was too. He didn't mind if it meant that he didn't quite fit in with the other kids in his classes. The smiles he earned from his family with every A was enough. Even if they tended to focus more on his brother's bad grades, this was understandable. Why would you put your attention on something close to perfect, when there was a problem they needed to place it on? In this case, it was worse to get attention, as it meant you were trouble, a burden, something that needed to be fixed. At least, this was how Luke saw it.
Either way, he loved his family. He attempted to be the perfect child and sibling for them, to make them proud. He didn't bother them with his problems, but instead worked as hard as he could to fix them himself. He strived towards perfection. Never was he a burden, never was he inconsiderate. He comforted when he knew he should, encouraged when needed. He even hung out with them when they were bored, though it bored him. He did everything to please them. He loved both of his siblings and his parents. He looked down upon those who would earn bad grades or cause trouble for attention. He felt that they should be content the way they are, they should realize how lucky they are to have a family at all. He pitied those who were without a family, or were part of a bad, 'unhealthy' family. To him, his world revolved around his family. No, his family was his world. He would sacrifice anything and everything for them. So, what would happen if his world were to fall apart?