There is no rule that the wife should be younger or shorter than the husband.
BV creatives never bothered to 'age' the parents when their children grew up. So Bhairo, Sumitra, Basant and Gahna still look the same as they were when Anandi and Jagya were less than 10 year old. Now Anandi- Jagya are in their late twenties but the look of older generation is still the same. So Shiv's parents also do not look "their" age. Who could say that Ira-Alok were actually celebrating their 37th anniversary? Even if Alok-Ira were 22 years old at the time of their marriage - their present age should be 59 years - even Ira does not look 59 years old. Daddu must be in his seventies or early eighties- does he look like one?
Daddu is older than Kalyani and taller than her also - so that augurs well for their future union !