Money – how it’s being spent, that there isn’t enough. Feeling financially stressed can cause all sorts of issues
Sex/Intimacy – Frequency of it, type
Kids – behavior, how to discipline, how the other ones handle a situation.
Chores / Responsibilities – Are you pulling your weight? One spouse often feels like they are doing much more than the other.
Work – Staying late, the complaints that come with it. The obligations and stress it causes. We can sometimes be pulled in two different directions. Spouses can build up resentment blaming everything on the job.
Habits – Leaving the toilet seat up, to dirty clothes being on the floor, to toothpaste cap not being on. I’d say in my house we actually don’t argue a lot about habits but the one could be music. My wife will play music really loud, especially in the morning. My kids and her love it and I can’t stand it. I need quiet in the morning.
Relatives / Extended Family – From the mother in law to the crazy uncle, the extended family doesn’t get unconditional love from the spouse. This can be a big source of friction. The rule iI was always taught is to stay out of your spouse’s family’s issues. Let each handle their own side.
Jealousy – Whether because they are spending time with someone else or they give their attention to someone else, jealousy can be a big source of arguments.
Free Time – what you do in your free time and how much free time you get. There often seems to be a discrepancy in how much free time each gets
Friends – One doesn’t like who the other hangs out with. The bad influence, taking time away from theirs