Original proposition: If one of me and him is not in front of you, then I am in front of you.
Negative proposition: If I am not in front of you, then we are both in front of you.
In this way, you can see that your original proposition itself has made a logical mistake, so your negative proposition has also made a logical mistake.
In addition, the truth of your proposition has nothing to do with your so-called "major premise". I hope you can sort out your logic. You can judge the truth of your two judgment propositions by the fact that I am in front of you, just as it is ridiculous for you to conclude that "if I don't eat eggs today, I will eat eggs today" is a true proposition.
"If ... then a hint"
To judge whether an implication is true, it is necessary to judge whether a proposition is true by assuming that the conclusion of the proposition is true.
If your original proposition is true and the conclusion "I am in front of you" is not necessarily true, then this proposition itself is a false proposition.
For more information, you can refer to unary logic, or you can find a book on discrete mathematics and read the chapter on logic.