They are not blood related and they had lived together just for a couple years in uke's high school days so I think there is nothing disturbing except age gap ┑(￣Д ￣)┍ even they had waited for seme's graduation to have sex and it is a very rare thing for a yaoi (●'◡'●)ﾉ so it is a good readლ(´ڡ`ლ)
They are not blood related and they had lived together just for a couple years in uke's high school days so I think there is nothing disturbing except age gap ┑(￣Д ￣)┍ even they had waited for seme's graduation to have sex and it is a very rare thing for a yaoi (●'◡'●)ﾉ so it is a good readლ(´ڡ`ლ)