The bottom has been Dom from the start. He just prefers true love over dynamic love because he can easily get "play" partners.
Like he said dom/sub being together is just fulfilling their sexual needs, alot of them don't even love each other, just the feelings of dom/sub.
And the top is also a sub since the very beginning. I think he was thinking of rejecting the bottom because he thought Bot is a sub and he can't fulfill him since top ain't a Dom. Then turn out they're perfect match.
And the reason why he even agreed to the blind marriage because he thought there'd be no love and just purely contract, until he finds himself liking the bottom so he doesn't want to drag things out (thinking Bot is a sub)
Hahhh???
Is he switch from sub to dom??
I felt anxious when reading the sex scene... Thought he will backstab the sister lol