Responses
Yeah they are related. Even his bride is related to him. If Hathor is the daughter of Ra, that makes Iris her grand-niece. So, better for Horus to be engaged with Seth, his uncle, than Hathor, his great-aunt. ╮( ̄▽ ̄)╭
As for the brother part, I also read some Egyptian mythology. It seems that Horus and Seth's relationship is ambiguous. They could in fact be siblings.
Looking forward to see how Ennead will depict their relationship.
Are they related i think I saw something saying they're brothers i don't know if I can read this if they are related Σ(  ̄□ ̄||)