Angular 6 - change checkbox style whether is checked

I have a list of checkbox and I want to underline the one that is checked. My code looks like the following:

TS file:

currentQuarter: string;
quarters: Observable<MeseRiferimento[]>;
q1: MeseRiferimento = new MeseRiferimento();
q2: MeseRiferimento = new MeseRiferimento();

ngOnInit() {
q1.desc = "One";
q1.id = "1";

q2.desc = "Two";
q2.id = "2"

currentQuarter = q1.id;
quarters.of([q1, q2]);
}

isQuarterSelected(q: MeseRiferimento): boolean {
return this.currentQuarter === this.getKeyFromQuarter(q);
}

HTML file:

<div *ngFor="let q of quarters | async" class="col-1 my-auto m-stati">
<label class="custom-control custom-checkbox ra-check">
<input type="checkbox" class="custom-control-input" [ngClass]="{'checked': isQuarterSelected(q) }">
<span class="custom-control-indicator"></span>
<span class="custom-control-description"></span>
</label>
</div>

CSS file:

.custom-control-input:checked~.custom-control-indicator {   
color: #fff;   
background-color: #3bb8eb; 
}

These are the issue with this code:
1. when I load the page, the default checked checkbox has correctly the class 'checked' but the CSS is not applied, i.e. it's not underlined
2. when I manually select a checkbox the class 'checked' correctly applies and the CSS too applies
3. when I manually select another checkbox, the class 'checked' correctly switches from one to the other, but the CSS of the former do not update, i.e. the previous checkbox remains underlined

Thanks for any advice.