I want to select only whose parents have display: block and exclude those whose parents have display
There are no such selector available in CSS to select by their property values. You can try something with jquery by using :hidden selector to find buttons with display:none. Check below snippet for reference.
$( ".btnShow" ).click(function() {
$( ".btn:hidden" ).show( "fast" );
});
.hidden{
display:none;
}
.btnShow{
display:block;
margin-top: 50px;
}