Uncle Scott was a civilian traveling with the 2nd Massachusetts Militia Regiment. Scott teaches the children biology, fixes a tube radio and discovers that the Skitters communicate on fluctuating frequencies. His suggested jamming repels an attack on the school. Scott dies protecting children in the Battle of Fitchburg, about a month after Tom is abducted by the overlord at the end of Season 1.
Scott is Anne's uncle, though it is never revealed whether he is a blood relative or if they're related solely through marriage. Scott, Kate, Anne and Sam went on a weekend trip to Lake Huntington, and while fishing with Sam, Scott caught a fish but as soon as he pulled the hook out it swam away. It can be inferred, that Uncle Scott was likely a teacher pre-invasion.
During Fitchburg, Scott and the 2nd Mass kids are forced to retreat with skitters and mechs on their tail. When a mech prepares to shoot at them, Uncle Scott throws himself in-front in an effort to let the kids gain more ground and escape. Scott is tore apart by mech bullets and instantly killed.