The Lord of the Rings star and Katy first hit headlines in January (16), when they partied together after the 2016 Golden Globes. They were then both spotted attending actor James Lecesne's one-man play, The Absolute Brightness of Leonard Pelkey, in Los Angeles last month (Jan16), and were pictured getting close at a Hollywood dinner party on Wednesday (03Feb16).

Now it appears the relationship is getting serious after Katy joined Orlando on Saturday (06Feb16) to take his son, Flynn, to a birthday bash for Robert Downey, Jr.'s boy, Exton, at the Iron Man actor's Malibu, California mansion.

"Katy was entertaining Flynn so he wouldn't get bored," a source tells "It was a long drive and she was talking to him and making him laugh."

"They were laughing, playing music and joking around with Flynn (at the party)," another insider adds to "They stayed at the party for hours. Katy looked very comfortable at the kids' party. She seemed very happy to spend the day with Orlando."

Orlando and Katy have yet to comment on the status of their relationship, but sources previously told the two enjoyed some "aggressive flirting" at Harvey Weinstein's post-Globes bash, saying, "Katy and Orlando were standing in the back of the party drinking Moet (champagne) and were aggressively flirting before leaving together. She was very flirty and laid on the charm."

The British hunk was previously married to Australian model Miranda Kerr from 2010 to 2013 and they welcomed son Flynn in 2011.

Katy divorced comedian Russell Brand in 2012 after two years of marriage. She was most recently linked to on-again-off-again boyfriend John Mayer.