Discuss relationships you are or have been in or that you know where the people involved are not duals, but seem happy. Preferably those who have kids.
Edit: I would also appreciate as much detail and description as possible. Some detail that sheds light on why you consider the people to be the types that they are is necessary for it to be considered a real data point.
I have lived with an LII male and IEI female couple who seem happy, relatively speaking. Two adult daughters. They run a farm and small business together too.