In the OG, they had one huge MU and were separated for 25 episodes, they reunited for Mullai's birthday, Dhanam brought Mullai over, after the celebration. they cleared the MU and promised to each other that they will never separate and will always be together. This was around episode# 315. Since then they did not leave each other's side. This was 11 months after they were married.
So they didn't confess? I mean I love you nahi bola bas dono ko samaj aa gaya ki they love each other?