Targetting first div in group with shared class name

[rajc08]

I want to target a div which is not nested and only select the first one which has that class name and hide others. See the screenshot below.

From the picture, you can see the layout of the code in HTML. I want to only target the yellow highlighted div and hide the others. Any help will be very much appreciate. Thanks.

.in-conversation {
    display:none;
}

.o-section .c-video-section-wrap .in-conversation-wistia:first-of-type  {
   display:block;
} 

[Archibald]

Shouldn’t that be:

.in-conversation-wistia {
    display:none;
}