WILL little Apple Martin soon have a sibling to play with? Parents Gwyneth Paltrow and Coldplay singer Chris Martin are said to be trying for a brother or sister for their 7-month-old daughter. Paltrow was recently overheard telling friends, "We’re working on it," Life & Style Weekly reports. The star is so "besotted" with Apple, a pal shared, "It wouldn’t surprise me if she had another baby by next Christmas." Reps for Paltrow did not return calls.