The 36-year-old actress, who adopted six-month-old Jackson in March, is planning to donate the little boy's outgrown garments to her "Snow White and the Huntsman" co-star's two-week-old daughter India, reported Femalefirst.
"I'm going to give Chris' daughter all my son's hand me downs," she said.
The "Prometheus" star, who has been single since splitting from her partner of nine years, Stuart Townsend, in 2010, gives her child priority over her movie career.
"I'm about to go and shoot the new 'Mad Max' film soon and when I heard that my son was coming in to my life I thought, 'I'm not going to want to go and make this movie, I'm just going to want to stay at home in my pyjamas and roll around on the carpet with him'," she added.