No built-in way of doing what you describe AFAIK.
Here's a quick-n-dirty script that will draw the parents' and all sibling's collider bounds when any child is selected:
public class Foo : MonoBehaviour
{
void OnDrawGizmosSelected()
{
//GetComponentsInChildren also returns components on parent
var colliders = transform.parent.GetComponentsInChildren<Collider>();
Gizmos.color = Color.green;
foreach(Collider col in colliders)
{
var points = GetBoundsPoints(col.bounds);
DrawPoints(points);
}
}
Vector3[] GetBoundsPoints(Bounds bounds)
{
Vector3[] points = {
bounds.min,
new Vector3(bounds.max.x,bounds.min.y, bounds.min.z),
new Vector3(bounds.min.x,bounds.max.y, bounds.min.z),
new Vector3(bounds.min.x,bounds.min.y, bounds.max.z),
new Vector3(bounds.max.x,bounds.max.y, bounds.min.z),
new Vector3(bounds.min.x,bounds.max.y, bounds.max.z),
new Vector3(bounds.max.x,bounds.min.y, bounds.max.z),
bounds.max
};
return points;
}
void DrawPoints(Vector3[] points)
{
Gizmos.DrawLine(points[0], points[1]);
Gizmos.DrawLine(points[0], points[2]);
Gizmos.DrawLine(points[0], points[3]);
Gizmos.DrawLine(points[1], points[4]);
Gizmos.DrawLine(points[2], points[5]);
Gizmos.DrawLine(points[3], points[5]);
Gizmos.DrawLine(points[4], points[7]);
Gizmos.DrawLine(points[5], points[7]);
Gizmos.DrawLine(points[6], points[7]);
Gizmos.DrawLine(points[1], points[6]);
Gizmos.DrawLine(points[2], points[4]);
Gizmos.DrawLine(points[3], points[6]);
}
}
```