The most common une is Google, simple to use, does not fail and will install in the most common platforms. Anything else can be risky, except perhaps the Microsoft system that is more corporate oriented.
Same with you brother. I do think google authentication application is very reliable and yet very easy to be used. Since I do think it's safe, all of my emails are saved in it also my accounts. But I don't know if apple user's or mac trusts google same way we do.