Although neither of the celebs have admitted they are dating, rumours they were romantically linked started swirling earlier this year after they reportedly met up after the Golden Globes.
“They both share the same low-key vibe ... They've been secretly meeting up since they first got together,” a source told OK magazine.
They added: “They'll have quite a blended brood, but I imagine all the kids will get along great.”
Brad split from Angelina Jolie last September. The estranged pair share six children: Maddox, 15, Pax, 12, Zahara, 11, Shiloh, 10, and eight-year-old twins Knox and Vivienne.
Kate Hudson ended her engagement with Muse singer Matt Bellamy in 2015.