Personality
Marshall, because of his military upbringing and parenting, was a mostly serious child, taught to handle business first, and play hard later. Though, he got into trouble with his parents when they weren't around to watch him, mainly because he wanted to see what happened if he didn't always follow the guidelines his parents set for him, like any other child. He had to learn to hide his mischievous streak, keeping it in check through his younger years, only releasing it once he started college and his officer commission. He's rather methodical, opting to think through his problems than charge straight in, though he is known to go all-in when really pushed to do so, screaming all the way. He's proud of his service to the military, but occasionally wonders about what his life would be if he had just opted to stay out of the military, like his parents thought he would. He also feels out-of-place due to his new enhancements he volunteered for, wondering if it was worth it. He leans yes most of the time, though he feels he could deal without the stares he sometimes gets.
Background
Marshall joined the military to join the fight against an alien invasion of Earth, and joined as a rookie, climbing his way through the ranks through missions, and driving the aliens back. While doing so, he volunteered for Psionic training and Genetic enhancements, and it was found that he had an aptitude for mental abilities.
Marshall was an average child, living in a heavily sprawling urban metropolis, born to military-serving parents; his father was an infantryman, and his mother was a communications specialist, leaving the child's path mostly set for him, at least, that's what he thought. He got intro trouble like every other child, though his parents' brand of discipline seemed a lot rougher than his friends' and classmates', though for more reasons than he had initially thought. He was pushed to do well in school, to give him an out of the military; to his father, he didn't want to risk losing his only son to combat, having lost friends, and even himself, to it. His mother was equally as reserved about Marshall going into the military, and would have been content with him becoming a doctor.
For a while, Marshall was entirely uninterested in joining the military, though during high school, he found that some of his interests were mixing in with the military - space exploration - and he decided to join after he graduated and attended College, majoring in Aerospace Engineering, and obtaining an Officer commission, and working with Superia's Air Force. His parents supported his decision, but not without their worries. Marshall would initially work as a technician, but was put through combat training to aid against an impending Alien Invasion, and allocated to the newly established Extraterrestrial Defense Division. Marshall would get a taste of combat; but instead of against people other people, he was thankfully (or not, Marshall wasn't that eager) against otherworldly beings. The young man helped to fight the invasion back, and opted to volunteer for new experimental procedures in Psionics and Genetic Engineering, out of a sense of obligation to the friends he lost, the people he said he'd protect, and out of an interest in what seemed to be advancements out of a science fiction novel.
Eventually, they drove back the alien menace, though a lot of things had changed in such a short time, with new advancements in technology reverse-engineered from the aliens, to Marshall himself, who had matured considerably. He was more stoic, but had come to appreciate life more since he had been in the military. He returned to his parents with open arms and tears, understanding fully the sacrifices they made for him.