It is the fact that no matter what, Saras will trust Kumud and she will trust him.
There will never be any jealousy track, because there is no possibility-even the faintest of Saras doubting her love for him.
Danny can suspect Kusum, but Kumud will never suspect Saras.
That is the beauty of this show. This one factor is missing in so many shows-as if jealousy is somehow proof of love.
Only this show shows jealousy for what it is-a negative emotion best kept away from one's life.