Is it permissible to call my brother "Majeed" as a diminutive for his name "Abdul Majeed"?

It is permissible to name individuals with names shared between creation and Allah, as long as the name is not exclusive to Allah (like "the Creator"), or if the attribute of Allah is not intended by it. This is evidenced by the Prophet Muhammad's (peace be upon him) approval of some Companions' names that involved this sharing, such as Ali and Hakim. Therefore, if a person is named Majīd (Glorious), there is no harm, because the name "al-Majīd" can be applied to a creature as a description of glory. As for names exclusive to Allah (such as: al-Khāliq (the Creator), al-Raḥmān (the Most Merciful), al-Quddūs (the Most Holy)), it is forbidden to name oneself with them.