Moon's feed

i just remembered something…
in the earlier chapters the mc(yeongwon?) mentioned that Haeyool looks very similar to seo in’s brother..

if thats the case, why is seo in and his cousin(the sponsor) having sexual relationship with haeyool. so the whole family is having incestous vibes towards the dead brother or what?? like, why are you fucking someone who looks like your dead relative/brother?