Angular 2 の兄弟コンポーネント間で通信するにはどうすればよいですか?

@Injectable()
export class SharedService {
    dataArray: string[] = [];

    insertData(data: string) {
        this.dataArray.unshift(data);
    }
}

import {SharedService} from './shared.service';
@Component({
    selector: 'parent-component',
    template: `<child-component></child-component>
               <child-sibling-component></child-sibling-component>`,
    providers: [SharedService]
})
export class ParentComponent { }

import {SharedService} from './shared.service'
@Component({
    selector: 'child-component',
    template: `...`
})
export class ChildComponent implements OnInit {
    data: string[] = [];
    constructor(private _sharedService: SharedService) { }
}

import {SharedService} from './shared.service'
@Component({
    selector: 'child-sibling-component',
    template: `...`
})
export class ChildSiblingComponent {
    data: string = 'Testing data';
    constructor(private _sharedService: SharedService) { }
}

addData() {
    this._sharedService.insertData(this.data);
    this.data = '';
}