Actors Tom Holland left, and Zendaya poses to the media during a photocall to promote the film Spider-Man: Home coming" in Barcelona, Spain, Sunday, June 18, 2017. Picture: AP

The 'Spider-Man: Homecoming' co-stars reportedly fell for one another while making the movie, and though they have been trying to keep their romance out of the spotlight, insiders claim they have been spending a lot of time together.

A source told People magazine: "They started seeing each other while they were filming 'Spider-Man'.

"They've been super careful to keep it private and out of the public eye but they've gone on vacations with each other and try and spend as much time as possible with one another."

READ: Spider-Man - Homecoming Review

16 days. Thank you @craigmcdeanstudio and @interviewmag for mixing it up at little bit.

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The 21-year-old actor and the 20-year-old actress "challenge" one another but they also have a lot of fun and are always "joking around" together.

The source said: "They're both really ambitious and they challenge each other -- but, most importantly, they make each other crack up. They seem to have a really similar sense of humour and love joking around together. They have great banter back and forth."

Tom previously described Zendaya as his "best friend" and praised her for helping him navigate fame.

He said: "We are like the best of friends. She's so great and amazing.

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"I'm a little worried [about dealing with fame ... but] Zendaya is super famous and she's been through this and I just call her up and say, 'How do I manage being famous?' I'm very glad I have a friend like her."

The pair wouldn't be the first 'Spider-Man' co-stars to enjoy an off-screen romance.

Kirsten Dunst and Tobey Maguire embarked on a relationship while shooting 'Spider-Man' in 2002, but had split before filming the third installment in 2007.

And 'The Amazing Spider-Man' co-stars Andrew Garfield and Emma Stone enjoyed a three-year romance until 2015.