It is very easy to prove that Rhaast/Kayn canon. Look. . .
Rhaast is already inside him.
Perfectly.

seen from Maldives
seen from Australia
seen from United Kingdom

seen from United States

seen from Maldives
seen from United States
seen from China

seen from Maldives

seen from Malaysia

seen from United States
seen from United States

seen from Martinique
seen from Croatia
seen from China
seen from China

seen from China

seen from United States

seen from United States

seen from United States
seen from Fiji
It is very easy to prove that Rhaast/Kayn canon. Look. . .
Rhaast is already inside him.
Perfectly.
Kayn: Once you ask me who I love more — you or the risk. I will answer: "Risk!". You'll leave without realizing that you are my risk. Rhaast: Disgusting. Rhaast: I love it.
sequel
Kayn: I'm sleeping with Rhaast.
Zed: ...
Kayn: ...
Zed, looks at the scythe: Mmm... What is it like?
Kayn: Well ... Not without difficulties.