In English, when someone says they are "one of" any number, that means that they are one of that many children. So a person who is "one of six" means that their parents have six children. The person speaking has five brothers and sisters.
"THE parents play" estus "LA gepatroj ludas".
Gepatroj ludas = (some) parents play
Vi povas forigi la "some". (You can omit some. They used it to show that you can use indefinite articles in English while in Esperanto you can't.)