ErrorException: Undefined array key "fname"

Guys, I'm using Inertia with React and Laravel Fortify to create a new user in the admin panel, with the roles many-to-many. I split the name fields to first name (fname) and last name (lname). However, whenever I try to register the user, I get the error ErrorException: Undefined array key "fname". Yet, on my register page localhost:8000/register, the same technique works so perfectly.

Here's what I have in my store() method:

public function store(Request $request)
    {
        $newUser = new CreateNewUser();

        $user = $newUser->create($request->only(['name', 'email', 'gender', 'mobile_number', 'password', 'password_confirmation']))->roles()->sync($request->roles);

        // dd($user);

        return back()->with('message', 'User has been created successfully.');

    }

In my Fortify Actions CreateNewUser class, this is what I have in the create() method:

public function create(array $input)
    {
        Validator::make($input, [
            'fname' => ['required', 'string', 'max:100'],
            'lname' => ['required', 'string', 'max:100'],
            'email' => [
                'required',
                'string',
                'email',
                'max:255',
                Rule::unique(User::class),
            ],
            'password' => $this->passwordRules(),
            'gender' => ['required'],
            'mobile' => ['required', 'max:30'],
        ])->validate();

        return User::create([
            'name' => $input['fname'] . ' ' . $input['lname'],
            'email' => $input['email'],
            'gender' => $input['gender'],
            'mobile_number' => $input['mobile'],
            'password' => Hash::make($input['password']),
        ]);
    }

My inputs have the name attribute fname, lname, gender, mobile, email, password, password_confirmation. I really cannot tell why Laravel is sending me this error message. Any help regarding this is welcome. Thanks team!