Niall Horan enjoyed secret dates with Amy Willerton.
The One Direction star is said to have started seeing the British model and former Miss Universe contestant behind closed doors after they met in December last year but the pair were desperate to keep their friendship "under wraps".
A source said: "Niall and Amy have done well to keep their friendship under wraps.
"They're private people and don't want to highlight their celebrity friends where possible. Plus it would set tongues wagging about a relationship."
It is believed the 'Night Changes' hitmaker and Amy, 22, have stayed in contact while One Direction have embarked on their On The Road Again world tour but are yet to discuss whether their secret romance will blossom.
The insider told The Sun newspaper: "They stay in touch but won't see each other until Niall returns.
"They have never discussed getting together but they have a soft spot for each other."
Meanwhile, the 21-year-old singer's former band mate Zayn Malik - who announced he was quitting the group last week after five years - is reportedly planning to tie the knot with fiancée Perrie Edwards "as soon as possible".
The couple have been rocked by rumours the 22-year-old star cheated on the Little Mix singer in Thailand two weeks ago but are thought to be putting the allegations behind them and focusing on becoming husband and wife later this year.
A source said: "When Zayn proposed to Perrie nearly two years ago it was so he could marry her.
"Now though, he wants to make that right and get married as soon as they can plan the day they have been dreaming of."