The most common and most likely answer to this crossword clue is the 8 letter word SIBLINGS
I've seen this crossword clue in The Times
S
I
B
L
I
N
G
S
More clues leading to the result SIBLINGS
Buddy explains!
The straight part
We know that "Adults may have them/not only children" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case adults may have them/not only children = siblings.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does SIBLINGS mean?
SIBLINGS noun- A person who shares a parent; one's brother or sister who one shares a parent with.
- A node in a data structure that shares its parent with another node.
- The most closely related species, or one of several most closely species when none can be determined to be more closely related.