@icedquinn

no they are not, space marines are created via organ implantation and custodes are created via an _entirely_ separate process that mostly completely rewrites the genetic material of a very select few compatible babies taken as donations from inbred terran noble families, creating a custom-made transhuman

the space marines method is _explicitly_ only compatible with 13-ish young boys of a healthy constitution, whereas there's been no such discussion about custodes