adult toys being used as malware - SMARTPHONE
"Adult children" comes from "adult children of alcoholics", but now has broader reference to adults who were abused emotionally, physically or sexually in childhood. Etymonline comments: Specific sense of "adult male of the human race" (distinguished from a woman or boy) is by late Old English (c. 1000); implying that "man" was used in a purely non-gendered way before then.
Context Explanation
"adult children" is sometimes used in contexts where age is important, such as a form requiring someone to list all children under 18 and all adult children living with them. And someone might use it to emphasise that their children have left home or aren't dependent on them. But you wouldn't introduce someone as "my adult child/ren".