If you want to keep your son's Instagram account away from prying eyes, better not to follow his account.

That seems to be the lesson learnt by Hong Kong actress Cecilia Cheung, who inadvertently revealed the handle of her eldest son Lucas on Sunday (Sept 6) when she followed his Instagram account.

Lucas, 13, is Cheung's son with actor-singer Nicholas Tse and the couple have a younger son Quintus, who is 10. Cheung and Tse divorced in 2011 after a five-year marriage.

The 40-year-old actress has a third son Marcus who was born in November 2018.

Lucas used a photo of himself winking and using his hand to cover part of his face as his profile photo, with netizens saying that he looks like his father.

Under the bio description, he used the quote: "The positive thinker sees the invisible, feels the intangible and achieves the impossible."

Cheung has since unfollowed her son's account after his username was reported widely in the media. Lucas' account is also unsearchable on Instagram.

But his mother has written several posts on, and put up videos of, him and his brothers on social media.

In a post wishing Lucas happy birthday in August, Cheung posted a wefie with him with his eyes closed and another of their hands together on his 13th birthday on Aug 2.

She also posted a photo of Quintus when he turned 10 in May and another photo of her with her three sons together.