Transferring points between family members is free with Marriott, but there is quite a procedure. I've never done it but I found this in the Boarding Area blog, hope it helps!
"Marriott allows the transfer of points at the time of reward redemption only to a legal spouse or domestic partner. An Authorization to Transfer Points form must be completed and submitted to Rewards Program Guest Services in order to transfer the required number of Points. Forms are available by calling Rewards Program Guest Services at 1-801-468-4000 (Marriott Rewards Program) or 1-866-922-6882 (The Ritz-Carlton Rewards Program). A request for Reward Redemption from the transferee’s legal spouse or domestic partner must be submitted to Rewards Program Guest Services with the Authorization to Transfer Points form."