People who know how to make nouns plural in general often make up their own crazy set of rules when dealing with names:
I know two people who are Gonzalez’s, three Garies, two Barry’s and five Maxs.
Those should be Gonzalezes, Garys, Barrys and Maxes. Of course, you can just write that you have many friends named Gonzalez, Gary, Barry and Max. I can hear you breathing more easily.
People whose last name ends in a vowel are no different than your consonant-ending friends:
Castroes and Castro’s aren’t plurals for Castro. All you need is Castros.