Koi wa Futago de Warikirenai

Both shows explore the wrongs and harms of denying your feelings for the sake of other people's well-being, as well as forcing romantic relationships. Also, both anime raise the question of the difference between romantic and simple spiritual attraction to someone important to you. 

Although they have different storyline concepts, both of these anime portray a romantic story between the main character and their stepsibling. This theme often serves as the main focus of the story, providing both conflict and comedy throughout the series. Both Kiss x Sis and Koi wa Futago de Warikirenai are known for their mature humor and fanservice elements. These scenes are frequently shown as part of the romantic or comedic interactions between the characters. 

One is an anime, the other a gaiden OVA, but they have just about the same plot, almost as if one copied the other inconspicuously. Great for suckers for plots about complicated love between two twins... if there are many plots like that! 

Love triangle classic story, feel the same vibes with the characters and story 

Both shows start out as very melancholic, but gradually escalating into drama due to ill-considered romantic relationships and the characters' insincerity in their feelings. The main difference is that White Album is built around collaborative musical activities, while Koi wa Futago is centered around pop culture geek interests.