Gavin Rossdale: Kingston's a Little Bit Jealous of Zuma!

Gavin Rossdale says his newborn son Zuma is "fantastic. Really good."

And growing up - fast.

"He's counting backwards from 10, which is pretty impressive," Rossdale joked to Usmagazine.com Sunday at Jane Goodall's sixth annual Roots & Shoots Day of Peace.

Rossdale added that his two-year-old son Kingston is still getting used to being an older brother.

"Kingston thinks he's all right and is getting used to him," he said.

Any jealousy?

"I think at first there was probably a little concern that [Zuma] might be staying over!" said Rossdale.

Check out Us Weekly's babies of the year!

Meanwhile, wife Gwen Stefani "is feeling on top of the world," he said. "We went to a wedding yesterday for my manager's daughter. It was a lot of fun."

See what Gwen Stefani looked like pregnant.

On Friday, Rossdale blogged that life "is good, been having real good time adjusting."

"Every day is some sort of adjustment to the day before," he added. "It's been pretty busy on the home front, of course. There's been visits and people and precious time."

check out more from usmagazine