Why would you say that?
The odd thing about this meme is that everything is right. Anakin and Palpatine’s grandkids (Rey and Ben) do end up kissing. Anakin has done some pretty foul things (the younglings!), but his face in this meme shows utter disgust at the thought of an incestuous relationship between his own kids.
In The Empire Strikes Back, Luke and Leia lock lips. Unbeknownst to them, they actually share the same DNA since they’re both Vader children. In that kissing scene, even Chewie looks a little disgusted by their public display of affection. Later on, they play it off as being a brother-sister kiss, but a brother-sister kiss, it was not!