Don't have a daughter or a sister, but to answer your question, I wouldn't want anyone to be in a situation where they are forced to marry and it doesn't matter if the guy is the same age or much older, but if it did happen, I would hope that she finds happiness in the marriage. Marriage is not a game where you get married today and break it off tomorrow, it is serious business. And if someone I knew got married to a much older man and found happiness in the marriage, I would be rooting for them. Anyways, there are numerous examples of very successful marriages with age disparity, so I don't beleive a good and happy marriage is beholden to age in any way.
Like others have said, this show is a reflection of what happens in society, not the other way around. If it was then we could get rid of all the social problems by showing shows about them....because if a TV show can cause social problems, then surely it can get rid of them. Also, this is not an example of underage marriage, Santo was of the legal marriageable age(i.e. 18) when she got married....underage means that you are not of a legally marriagable age. The show is about how two unlikely people who are forced to get married find happiness in the marriage and make it work, not about how they got married in the first place and thats the spirit in which the show should be watched.
I am not quite sure what the comparison is with Pakistan and Canada.
And are you trying to say since it is 2009, relationships do not mean anything....that only blood relationships matter and not others, that people can go around disrespecting relationships and marrying whoever they want just because it is 2009....I don't think so. Santo is married to Hiten's fahter, furthermore Hiten has accepted Santu as his mother, that means Khemi is his maasi. Just because they are not related by blood, doesn't negate the relationship they share....just like adopted kids and stepkids are considered own kids even though there is no blood relationship....and saying that since it is 2009, it does not matter!!!!......it would matter even if it was 2059 because relationships have to be respected irrespective of the year you are living in.