Multiple Select with relationship in Builder Block is not working

Builder\Block::make('audio')
    ->schema([
    // …

        Select::make('voice_id')
            ->searchable()
            ->multiple()
            ->relationship('voices', 'last_name')
            ->createOptionForm([
                Forms\Components\Grid::make(2)
                    ->schema([
                        Forms\Components\TextInput::make('first_name')
                            ->required(),

                        Forms\Components\TextInput::make('last_name')
                            ->required(),
                    ])
            ]),
    ])