Markers that highlight by checkbox, and activate check boxes on click

I want to create map markers that, when clicked, highlight and also activate check boxes on the same page. I want the checkboxes to highlight the markers too. But that is a stretch target. So far I have a map with multiple markers at the right locations, popups stay open when clicked, but highlighting multiple and having the previous ones stay highlighted is beyond me. As is somehow linking them to the checkboxes.

I want the markers to stay on the map, but change appearance when clicked or when the corresponding checkbox is checked. Clicking the marker changes its appearance and also checks the corresponding checkbox.

Any pointers will be much appreciated. Code to follow (if deemed necessary.)