This is reproducible with marina b05, not reproducible with franca.

Run the below program. It shows a blue rectangle and a red rectangle in an HBox. When the blue rectangle is clicked, HBox triggers mouse events. But, mouse events are not triggered on clicking the red rectangle

import javafx.stage.*;
import javafx.scene.*;
import javafx.scene.input.*;
import javafx.scene.shape.*;
import javafx.scene.paint.*;
import javafx.scene.layout.*;

Stage {
    scene: Scene {
        content: HBox {
            content: [Rectangle {
                x: 0
                y: 0
                width: 50
                height: 40
                fill: Color.BLUE
            }, Rectangle {
                x: 0
                y: 0
                width: 50
                height: 40
                fill: Color.RED
            }]
            onMousePressed: function(e: MouseEvent) {
                println("mouse pressed");
            }
        }
    }
    width: 100
    height: 100
}