Is it permissible for a person to begin their letter with "To my dear father" or "To my honorable brother"?

It is permissible to apply the description "Al-Aziz" (The Mighty) to a creature, as Allah Almighty says: "There has certainly come to you a Messenger from among yourselves. Grievous to him is what you suffer; [he is] concerned over you, and to the believers he is kind and merciful." (Quran 9:128). And the Prophet, peace and blessings be upon him, said: "Indeed, the noble, son of the noble, son of the noble is Yusuf." These descriptions are not intended to convey the meaning specific to Allah, for the attributes of the Creator befit Him, and the attributes of the created befit them.