After months of playing it cool, Kate Hudson and Owen Wilson are turning up the heat on their romance – with his brother Luke's blessing

"He seems very happy," says Owen's younger brother, actor Luke Wilson. "[Kate] is a very nice girl."

Hudson, 27, and Owen Wilson, 38, have been opening enjoying each other's company recently. In Australia, where Hudson was working on the movie Fool's Gold, the pair shared bike rides and walks on the beach.

Now that they're back in the States, they're not letting jet lag cool their romance. Last Friday, the previously low-profile couple were anything but shy over lunch at Santa Monica's Ivy at the Shore restaurant.

"From the second they walked in, they were all over each other," says a witness. "Kate even [sat] on his lap to give him kisses."

The pair's new openness reflects a "natural progression" in the relationship, says a friend. Hudson, mom to 3-year-old Ryder, split with husband Chris Robinson last August.

"Owen has realized what a great thing he has," says the couple’s friend. "They're having fun, but things are definitely getting more serious."