You could use a sibling selector, but that is not as robust to changes being made in the DOM. Safer to use a common ancestor and find. For example, if the layout is changed for styling purposes and extra DIVs are added around elements, then sibling searches will fail.
You should understand the use of closest , it's job is to go upwards through its parent elements, NOT SIBLINGS, in your markup the class PhotoPicker is a sibling element, not a parent/ancestor element.
But addImage is a parent/ancestor element to imageclick. So you can access this using closest like this;
and then you can use the find function to get the PhotoPicker element inside it like: