Hover Effect that Affects Two Different Blocks at the Same Time with Different Effects for Each??

Hello,

I've been tormented for a while trying to figure this out. My goal is to have multiple text blocks and one video, and when a text block is hovered over, it changes the video to a different one. If not possible, then I'd like to have multiple videos each only connected to their corresponding text block.

My current issue is that I'm not sure how exactly I can have a hover effect affect two blocks at once with different effects for each. Is such a thing possible in squarespace or in the custom css section? 

I've been doing simple tests to try to understand how it might work, like this:

#block-c25f8a15bd4a31be8b38 {
  opacity: 1;
}

#block-1eb5cb072fcebafe2d23:hover #block-c25f8a15bd4a31be8b38 {
  opacity: 0.5;
}

but even this doesn't work, and I'm having trouble finding any relevant solutions online. 

Any help is welcome, thank you.

Can you share link to page? Sometimes we will need to use JS code to handle hover behavior