Matthew McArthur was born one snowy December day to two very well off people. Now his parents, of course, wanted to have a child but just weren't ready for the responsibility. After all, raising a child is a lot of hard work that they thought they could handle. That was their first mistake, to be honest with you. You see, sure they had the finances and the means to take care of him, just not the emotional capacity. The McArthurs were extremely selfish and honestly, only had room for themselves. A very toxic relationship indeed.
So you can only imagine the neglect Matthew was born into. Sure, he got all the things he wanted - minus his parents affection. In fact, this resulted in a magical outburst (several things blew up and/or shattered). This of course, resulted in nothing but a minor scolding as they replaced the broken objects. Which of course, wasn't what Matthew wanted. So after the destructive age of seven, he threw himself into his studies, foolishly thinking that if he was smart enough they'd spend more time with him.
By the tender age of eleven, he had received a letter and an unexpected visit from some oddly dressed person to break the news to the McArthur family. He explained about the world and showed them proof that it was, in fact, real and that Matthew was a wizard. This provided a small window of time full of affection and attention. However, it was gone before he was used to it and he spent the last month in Muggle London wishing to go to a school he's never been.
Once there, he was quickly sorted into (house). He threw himself into his studies and discovered an unfamiliar passion for the wizarding sport of Quidditch - and he was pretty good at it too. He joined his house team and somehow managed to handle both the rigorous training schedule and ever growing pile of essays and homework. Which of course, never left any time to socialize. He didn't mind though. He was used to it by this point in time.
He was quickly recruited for Puddlemere United, which he quickly accepted, seeing a chance to leave his oh so wonderful life behind. He didn't expect making any friends with his team or even meeting a girl he would be even remotely interested in. Matthew also didn't expect to slowly be brought out of his antisocial shell around these people.
But hey, life is often unexpected after all.