Not too sure if these two pictures should be tagged as related posts, what sort of relationship (parent post, child post / etc ?) or how to go about doing it. They are essentially the same except one has cum dripping out of her and the other doesn't. Sort of coitus / post coitus shots.

No cum

https://e621.net/post/show/685853/brown_hair-canine-censored-clitoris-cub-dog-duo-fe

Cum

https://e621.net/post/show/685854/brown_hair-canine-censored-cub-cum-cum_in_pussy-cu

Going by the picture numbers, the cum shot one was posted first and the no cum version posted immediately after.

I usually parent the cum version to the no cum version.
To do this, go to the non-cum version and at the bottom of the image, click the Edit button. There is a field titled Parent Post ID, put the cum version's ID in that field and click save.
If you need to unparent a image, just delete the text in the Parent Post ID field and it will be unparented.

Hope that answers your questions! :3

it doesnt really matter and post ids matter even less in this stuff. but most commonly no-cum version is parent

I personally go with the "sex/scene timeline" so I'd make the nocummy version as the main one and the other one as child

I think a child post is supposed to be created by modifying the parent post. So a picture without cum (post #548708) is the parent, and the version with cum (post #548709) is the child. The one without a penis (post #548708) is the parent, and the one with (post #548710) is the child.

This contradicts the chronological strategy in the case of clothed vs nude versions of a picture. My thinking is that the clothed version (post #548707) is created by drawing clothes on top of the nude version (post #548708), so I make the nude version the parent.

A screenshot from an animation (post #756424) is the child, except if the animation was created from a still picture (post #103886). A collection of scenes (post #1021182) is the parent of its component scenes (post #879598, post #879599 and post #879600). A redrawing (post #899302) of an old post (post #75051) is its child.

Ok, cool! Looks like someone already did it. :D Thanks all!