Am I sinful for going against my mother’s wish to name my younger brother “Ali,” fearing falling into the polytheistic glorification that my mother and some of my female relatives believe, that the names “Muhammad and Ali” protect the house?

It is advisable to respond to the mother's request to name the newborn "Ali," as it is a good name, while striving to change the corrupt belief with wisdom and gentleness. A Muslim must believe that all affairs are in the hand of Allah alone, and that He is the One who benefits and harms, as stated in His saying, the Most High: "Say, 'Who provides for you from the heaven and the earth, or who controls hearing and sight and who brings the living out of the dead and brings the dead out of the living and who arranges [every] matter?' They will say, 'Allah.' So say, 'Then will you not fear Him?'" (Yunus 31), and His saying: "Allah knows what every female carries and what the wombs lose [prematurely] or gain. And everything with Him is by due measure." (Ar-Ra'd 8). The Sharia (definition) has prohibited ill omens, for the Prophet, peace and blessings be upon him, said: "There is no evil omen, and the best of it is optimism" (narrated by Muslim). The name of our noble Prophet is among the best of names, but merely having a good name does not benefit its owner if he is corrupt.