Couple - Can I say I have a couple of kids meaning that I have a girl and a boy, or it is only for number, not gender?
See, you can't say:
We're a couple of people.
to express that you and your husband are a couple (a man and a woman). The way you say it would be:
We're a couple.
The same rule counts for a couple of kids in your question. That doesn't mean that there are a boy and a girl. That also isn't saying that there are literally two kids. A couple of something means there are 2, 3, 4, ... of that something.
only for numbers. Couples can be same-sex too.
You can say you have a couple of kids if you have two children, but that doesn't imply a biy and a girl, just that there are two of them.