sorry about the bad news scott.
Sepsis just describes bacteria in the blood. It means that a localized infection has entered the bloodstream and now circulates throughout the body, affecting everywhere. The reason it is harder to treat is because you have to treat the initial infection, and the rest of the body.
Enough with that. It sounds like this is your brother's monitor. Now I have some things to say about your parents... like why are you two kids allowed whatever pet you desire? And when it is clear that they aren't in the best of care (a burned savanna, a dead ball python, a dying monitor) they continue to allow them; and NEW ones?
In anycase, you can't avoid the situation you are in, nor the lack of knowledge/interest your parents have. It is time you become a young adult and take control of the situation. This animal needs treatment or humane euthanasia. It is suffering. It may be your brothers but you see the need, he doesn't. Tell your parents of the situation, and insist on a vet visit. If this falls on blind eyes then contact your local humane society to remove the animals and have them treated accordingly. Part of growing up is realizing that the needs of the animals have to come first.
If this still isn't clear; Do what ever it takes to see that this monitor sees a veterinarian.