"Kate really wanted another baby," the source says, adding that the father of Hudson's unborn child, British rocker Matthew Bellamy, is "a great person to do that with. He's a very good person."
And what makes the pair tick? Another source says the two make sure to inject fun into their romance.
"He loves Kate's carefree attitude," the source says, "and [he] has a lot of fun with her."
Hudson, 31, who has a son, Ryder, 7, with ex-husband Chris Robinson, has been dating Bellamy, 32, who fronts the band Muse, for about nine months.