Jessica Biel says "baby brain" is making her forgetful.

Justin Timberlake and Jessica Biel

Justin Timberlake and Jessica Biel

The 38-year-old actress gave birth to son Phineas last year but confessed that motherhood is taking its toll on her memory while promoting her new TV series 'Cruel Summer'.

Jessica - who also shares son Silas, five, with husband Justin Timberlake - forgot to answer a question at the Television Critics Association virtual panel and quipped that it was due to "baby brain".

'Cruel Summer' marks the star's first project since giving birth last year and she serves as an executive producer on the 1990s set drama, which stars Olivia Holt, Chiara Aurelia and Blake Lee.

Justin recently explained how he and Jessica have needed to adapt to having two children to keep an eye on.

The 40-year-old pop star said: "His name is Phineas, and he's awesome and so cute, and nobody's sleeping.

"But we're thrilled. We're thrilled and we couldn't be happier. Very grateful."

Justin also likened the process of looking after the two boys to adopting NFL tactics.

The 'Mirrors' hitmaker said: "It's a lot of fun but I guess the saying goes, 'Go from a zone defence to a man-to-man very quickly.

"'You go get that one, I'll get this one.' But it's great and Silas is super excited. Right now, he's very much liking it but, you know, Phin can't walk yet or chase him down, so, I don't know, we'll see what happens."

Justin previously said that he didn't want to be "weirdly private" about his kids.

The star said that he doesn't want to hide his children from the spotlight but is also "conscious" about their privacy.

He said: "I try to be conscious of making sure we can live a life where we're not weirdly private but we're conscious of making sure they can be kids for as long as possible. And not have the weight of somebody else treating them differently because of something that their parents do ...

"For guys like us, you know, the hope is that we just keep instilling in them that we got really fun jobs, but it's not who we are. Hopefully down the road, then that has more weight to it I guess."