We all have in-laws. On both sides. I think it's a somewhat cruel twist of nature that one couple gets two pairs of in-laws. Really, they should do something about it.
I believe that upon each marriage, there should be a lottery and a random new set of parents is given to the couple. Consider it a new tribe. Now don't get my wrong. I love my in-laws, as does my husband, but think about the sanity involved in one set of grandparents per couple. There will be no over-caring for one spouse or the other. They may, quite possibly, not care for either.
This goes double for mixed-cultured marriages. There's so much confusion with the two sides and getting used to your spouse's parent's ways. Take my Brazilian to American marriage for example. I think we should be given a set of German parents. That way we are all equally confused.
And that would banish the whole "I don't get your Mother/Father" situation totally. For starters, it would not be offensive to say something along the lines of "I hate when your Mother/Father does this!" because they would probably agree. That or, at the very least, they wouldn't get butt hurt by the comment. A lack of history is great at keeping you unbiased.
Not to mention it would be a fabulous way of meeting new people and internationalizing the world.
So who's up for a lottery? I can offer some grade A parents on both sides!