It is for FANS to support Xscape not Jackson family members including Michael's children.
Jackie works in some capacity with the Estate so it is logical he would tweet about it. Even when Michael was alive, he did not publicly state "buy my sister's Janet's cd" as that would be deemed unprofessional and a form of nepotism that the media would never forgive any Jackson for. Michael would circumvent that by always saying which song by Janet he loved to dance to.
Thank you. Timberlake is stating on Twitter he is honored to be on a Michael Jackson song and will be discussing it in several interviews most likely. Jesse is understandably angry as he finally received the honor of working on a Michael Jackson record and no one will hear it. HFITS had quite a bit of talent on one song so it is a waste not being able to hear it on Xscape. It would have been grand for the bonus song to be an unheard song. Instead we have the Anka dream listing. (I could not resist typing that last sentence.) laughs