What is the difference between the levels of Paradise, and is raising a servant's status to unite him with his parents in Paradise an injustice to others?

The ranks and levels of the people of Paradise vary, and the bliss of the highest ranks is superior to others. This does not contradict the fact that the people of Paradise will have everything their souls desire, for this desire is related to their own Paradise and their own station. All the people of Paradise will be content with the perpetual bliss that Allah has bestowed upon them, and there will be no yearning or envy among them. Rather, "We will remove whatever is in their breasts of resentment." Allah may unite a believer with his offspring and spouse in Paradise, elevating the lower in rank to the higher. This does not entail injustice to those who remain in their stations, for it is from the grace and generosity of Allah, which He bestows upon whom He wills.