What do you call an old man who has never been married?

bachelor. noun. a man who has never been married.

What to call the person youre probably never going to marry?

Fiancé What Do You Call the Person You Are Probably Never Going to Marry? Your Fiancé.

What do u call your partner when engaged?

These two words are borrowed directly from French, in which language they have equivalent but gendered meanings: fiancé refers to a man who is engaged to be married, and fiancée refers to a woman.