I am sorry if I wasn't clear.
I have seen it somewhere, which says if an apostrophe is followed after the word that ends with "s", it takes a plural form.
If i get to see that info again, I will certainly let you know.
Thank you and sorry for bothering.
***** NOT A TEACHER *****
Please feel free to post as many questions as you wish. That is why
this website exists: to help sincere people like you who have questions
about the international language.
Maybe (maybe) you are talking about this:
There are two boys. The two boys own one automobile together. They
each contributed $5,000 to buy the $10,000 car. So we can talk about
the boys' car. = the one car that belongs to the two boys.
If each boy had his own car, then we can say: the boys' carS.
(BUT: this could also mean that the boys jointly own two cars. That is,
they each contributed money to buy the two cars, which belong to both
of them.)
The child's toys. = the toys of one child.
The children's toys. = the toys of two or more children.
The use of apostrophes is difficult. Many native speakers do not
understand, either. The people at this website are delighted to
answer any questions that you may have.
Have a nice day!