Do your in-laws show up unannounced at all the wrong times? Do they demand to share all of your vacations? When your spouse is not around, do they criticize you or order you around? When your children are around, do they undermine you?
It can help to see things through their eyes. A long time ago, a tiny infant was placed in their care. They were charged with keeping this tiny child safe and fed. As the baby grew, it was their duty to teach them right from wrong. Maybe they taught what their parents taught them. Maybe they rebelled against what they were taught and emphasized different values. But it was a sacred duty.
Surely, they screwed up at times. We all do. And they had to do it while their parents and their in-laws continued to push the values that matter most to them: duty, respect, love, liberty, fairness, happiness, enthusiasm, piety, loyalty, learning, music, art, physical fitness, self-sufficiency, appreciation of the finer things, courage, whatever mattered to them. But the sum total of their efforts is the human being you admire and fell in love with.
And now it is your turn to navigate the confluence of your values, your spouse's values, your parent's values, and your in-laws' values, quite possibly while honoring that most sacred duty of teaching the most important of these values to a child.
It's not an easy journey for most of us. We could use a guide. Anyone with different values from your own who has gotten through this and managed to raise the sort of person you chose as your spouse is a great candidate. Consider asking you're in-laws, when you're not frustrated by their behavior, how they managed it.
And when you do find yourself frustrated by whatever your in-laws are doing, when they appear to be violating whatever you hold dear, consider stepping back to figure out which value they are fighting for and whether it's one that contributes to your spouse's good character.
This just might reduce your frustration level. If it does not, remember that it's perfectly fine to set your own boundaries now that you are an adult. You may not be able to tell them not to drop in unannounced if that is something your spouse values, but you can let your spouse know that when they do drop in, you'll be in your garden or watching television or out for a walk. And you can do it without anger, the same way you might go cook something while your spouse watches a football game or you might take the kids outside while your spouse's book club visits.
When you are criticized, you can acknowledge the value they are arguing in favor of and tell them what matters to you: "I know the men in your family are all great at hunting, and you all enjoy it a lot, but the world needs art, too, and that's what I'm good at and plan to focus on" or "I agree that cooking appetizing meals is very important, but today I am focused on getting some important work done to pay our health insurance bill, and I would love any help you can give me to get back to it."
For your spouse, who loves both of you, these work a lot better than "How can you think it's fun to take the lives of innocent animals?" or "Mind your own business and go eat at your own house if you don't like what I'm cooking!" And, at least for me, they feel a lot better to say, because they leave room for enjoyable future conversations without giving an inch on decisions that are mine to make.