Should I require starting name with a capital letter in form

I'm part of a team developing small web app. I'm responsible for frontend part of it. We've got form with inputs for user name and last name. Backend guy made a regex that requires name to be at least 3 letters long and it must start with a capital letter. I guess reason for it was for purpose only, but let's say it's necessary.

What type of frontend validation should I use? I'm thinking:

  1. Require by regex that user types his name with capital letter - but I know some people just don't care and type everything in lowercaps, so my thinking is it might scare some of them off

  2. Dynamically autocorrect first letter to capital with js

  3. Correct first letter to capital in backend

I think option 2 is best, but what do you think?