@Psychopath
I'' sure Raym's mom is dead and she was eunhyuk's piano teacher, Raym hoped that eunhyuk's father was her father (i mean they had an affair) but Raym was wrong and hence they are not half siblings like she hoped for.
So i think raym and eunhyuk got close and eunhyuk said that he will be his oppa/brother .
