Idk I have this headcanon in my mind (can be completely wrong) that Osiris was the oldest out of four siblings, then there was Isis and idk if Nephthy or Seth is younger but they were the younger ones. Osiris was the kind, intelligent and beloved first born who everyone had crush on, meanwhile Seth was troublemaker. Both Nephthy and Isis had feelings for Osiris, meanwhile Seth was secretly in love with Nephthy (or maybe not so secretly I can imagine him being quite obvious, being embarrassed and blushy, stuttering but he believed he was hiding it well but in fact everyone knew around him) but Nephthy didn't feel the same way for her Seth acted like rebellious kid and he wasn't as perfect, immaculate, elegant and serious as Osiris. But in the end Osiris chose Isis and Nephthy out of duty agreed to marry Seth. And it's heartbreaking because its clear Seth loved her dearly, he even thinks about her after centuries but I think although she was fond of him in some way, she didn't love him in romantic sense and was always in love with Osiris.
Idk I have this headcanon in my mind (can be completely wrong) that Osiris was the oldest out of four siblings, then there was Isis and idk if Nephthy or Seth is younger but they were the younger ones. Osiris was the kind, intelligent and beloved first born who everyone had crush on, meanwhile Seth was troublemaker. Both Nephthy and Isis had feelings for Osiris, meanwhile Seth was secretly in love with Nephthy (or maybe not so secretly I can imagine him being quite obvious, being embarrassed and blushy, stuttering but he believed he was hiding it well but in fact everyone knew around him) but Nephthy didn't feel the same way for her Seth acted like rebellious kid and he wasn't as perfect, immaculate, elegant and serious as Osiris. But in the end Osiris chose Isis and Nephthy out of duty agreed to marry Seth.
And it's heartbreaking because its clear Seth loved her dearly, he even thinks about her after centuries but I think although she was fond of him in some way, she didn't love him in romantic sense and was always in love with Osiris.