The family of the latest young person to die of a suspected overdose at a music festival has pleaded with NSW Premer Gladys Berejiklian to show ''strong leadership'' and introduce pill testing.

Central Coast teenager Alex Ross-King, 19, died after taking a suspected dose of pills at the FOMO festival in Parramatta at the weekend.

Ms Ross-King is the fifth young person to die at a music festival in recent months. Credit:Facebook

Family members of the teenager have pleaded with the government to introduce pill testing in "legacy" of her death, with grandmother Denise Doig worried her granddaughter's death will "just pass by".

"Premier, please: can we have this pill testing done. It's such a small thing to do, it's not hard. Let's try and get it out there," Ms Doig told Network Ten on Sunday. "If it saves one life; one life is a life. And these are children."