I'm looking for a yaoi manga where the seme forgets about the uke, but is still attracted ...

I'm looking for a yaoi manga where the seme forgets about the uke, but is still attracted to him and he thinks it's because he is attracted to the uke's sister since they look alike. He ends up finding the uke playing with himself, they do it. Later on the seme finds a recording of the uke & him doing it and he realized that they were together. Sorry, I'm not that good at explaining the manga thanks in advance. (●'◡'●)ﾉ