Families can have a type of language. Not that it is completely different than the language of their country, but that they may have 'invented words' or phrases. Or if the children have parents coming from different countries, they could speak rather in a 'mixed' language of those two countries. It would be nice if people made dictionaries of their family languages, so people could see funny words and phrases used by them. If you have some experience of this subject, I would be grateful if you would tell me more about it.
My family sometimes uses words in unusual ways. For example:
The word "umang" means "hermit crab" in Tagalog. In my family, this is what we call somebody who borrows clothes from someone without permission. One time I wore my sister's sweater and someone took a picture of me and posted it on facebook, and my sister saw it. I got caught being an umang. We also use it as a verb. "Do you know where my blue jacket is?" "I saw it in Crystal's car. She must have umanged it."
We use "floor shrimp" as a euphemism for cockroach. A few years ago, two buffet-style restaurants near where I lived had health violations at the same time. One had roaches while the other got in trouble for having an open crate of shrimp on the floor. One of those restaurants came up in conversation once and my brother asked whether I was talking about the restaurant with the roaches or the floor shrimp, and then he pointed out that roaches are basically floor shrimp. Ever since then, that's what we've called roaches.
Dilis is a type of dried anchovies that people eat in the Philippines. My mom says that she has to use a special kind of lotion or else she'll be "dilis," as in dried and shriveled up.
For multicultural communities like those with duolingo,slang language does harm and does not benefit.Also,professional style of language may differ than the social style but both are recognized.I think that dialects inside families varies,where you may meet a dominant or recessive one.