Complaining to your spouse about their family is only going to make them feel embarrased and will cause friction in your marriage.
You are spending the rest of your life with your spouse, there for you are spending the rest of your life with their family in your life as well.
So criticizing them for whatever reason you will only hurt your marriage. It won't hurt your spouse family, because chances are you wouldn't criticize them in front of them, so you are just hurting your spouse. Therefor your marriage.
Words are a powerful thing.
Be careful what you say, because words are seed. It will either grow or die.