43.5 answered your question about Doujin's mom
http://www.mangago.zone/read-manga/love_is_an_illusion/uu/love_is_an_illusion-chapter-43.5/3/
His mom is a man
http://www.mangago.zone/read-manga/love_is_an_illusion/uu/love_is_an_illusion-chapter-43.5/3/ the author confirmed that the mom is a guy. And yes the mom is the person wearing that blanket over their shoulders. Im guessing the author used female pronouns since he's the "mom" figure but idk it might be a mistranslation. About the nephew idk
So the word used in Korean was 사모님, which is two things: Really formal and under normal circumstances is translated to mean madam or ma'am. However, the term is technically meant to be used to address the spouse of the head of household. Obviously, in Korea same sex marriage isn't a thing so most guys would never be a 사모님. In the omega verse, it doesn't matter so Dojin's Mom can be both male and a 사모님.
haha its hard to believe huh? it was mentioned here http://www.mangago.zone/read-manga/love_is_an_illusion/uu/tr_chapter-5.1/pg-11/
Im assuming Dojin's mom is the person who wears that fabric over their arm but I honestly dont know anymore. Someone said hes a guy but then their maid said Ma'am. Also who is the Nephew's parents?