Jared was always the stupid twin, the bad twin, the difficult twin. Turned out most of it was having undiagnosed and untreated ADHD, and being made the scapegoat of the family when he didn't actually do anything wrong. Discovering Great-Grandpa Arthur Spiderwick's field guide to all things faerie ended up being the best thing that ever happened to Jared, despite all the hardships that came with it in the beginning. 

It wasn't until Jared had a teacher who actually paid attention to him in the eighth grade that ADHD was ever brought up to him, or Helen. Getting a diagnosis and being given tools to help him deal with it was life changing for him. Teachers were suddenly more patient with him, and willing to give him a little leeway to do things that would help him focus in class--like doodling in the margins, which he'd previously gotten in trouble for in years past. His mom was a little more understanding, but she was still often harder on him than she was on Simon or Mallory, and it kept their relationship strained. 

When they turned 18, Jared legally changed his last name to Spiderwick; he felt more connected to Arthur and Lucinda than the rest of his family, and certainly didn't want to keep his dad's last name. Simon changed his, too, but mainly because they were twins and he said it felt weird for them to have different last names. Jared kept less and less contact with his mother as he grew older; it was easier that way. 

Jared is currently working on getting a doctorate in folklore and mythology, as it's both something that genuinely interests him, and gives him an excuse to get access to older research materials he wouldn't otherwise be able to.