how to set the first author together?

Until the question will be more precise, this is my solutions.

First solution (using multiple authors and redefine title page)

Now each author has is command (you can easily expand to a lot of authors). All the authors have the same footnotemark and footnotetext.

Code

documentclass{article}

makeatletter
deffirstauthor#1{gdef@firstauthor{#1}}
defsecondauthor#1{gdef@secondauthor{#1}}
defthirdauthor#1{gdef@thirdauthor{#1}}
makeatother

firstauthor{John Doe}
secondauthor{Jack Smith}
thirdauthor{Jack Doe}
title{My Awesome Title}

begin{document}

makeatletter
begin{titlepage}%
  letfootnotesizesmall
  letfootnoterulerelax
  let footnote thanks
  nullvfil
  vskip 60p@
  begin{center}%
    {LARGE @title par}%
    vskip 3em%
    {large
     lineskip .75em%
      begin{tabular}[t]{c}%
        @firstauthorfootnote{The authors contribute equally to this paper.}
        and
        @secondauthorfootnotemark[value{footnote}]
        and
        @thirdauthor
      end{tabular}par}%
      vskip 1.5em%
    {large @date par}%       % Set date in large size.
  end{center}par
  @thanks
  vfilnull
end{titlepage}%
makeatother

end{document}

Result

Note on the usage with hyperref

All works fine, except a warning in the compilation and the fact that the footnotemark link on the second author is broken (that is the reason of the warning).

Second solution

I used the authblk package. Since I don't know which is the visual result that you would like, take a look at the documentation if you want to change the visual result. I modified the title-page only to insert the footnote without mark.

documentclass{article}
usepackage[affil-it,blocks]{authblk}


title{My Awesome Title}

author{John Doethanks{[email protected]}}
affil{First University}

author{Jack Smiththanks{[email protected]}}
affil{Second University}

author{Jack Doethanks{[email protected]}}
affil{Third University}

date{today}

newcommandblfootnote[1]{%
  begingroup
  renewcommandthefootnote{}footnote{#1}%
  addtocounter{footnote}{-1}%
  endgroup
}

begin{document}

%maketitle
makeatletter
begin{titlepage}%
  letfootnotesizesmall
  letfootnoterulerelax
  blfootnote{John Doe and Jack Smith equally contribute to this paper.}
  let footnote thanks
  nullvfil
  vskip 60p@
  begin{center}%
    {LARGE @title par}%
    vskip 3em%
    {large
     lineskip .75em%
      begin{tabular}[t]{c}%
        @author
      end{tabular}par}%
      vskip 1.5em%
    {large @date par}%       % Set date in large size.
  end{center}par
  @thanks
  vfilnull
end{titlepage}%
makeatother

end{document}

Result

If the first and second authors have exactly the same institution (department, institution and/or whatever) you could substitute

author{John Doethanks{[email protected]}}
affil{Some department, First Institution}
author{Jack Smiththanks{[email protected]}}
affil{Some department, Second Institution}
author{Jack Doethanks{[email protected]}}
affil{Some Department, Third Institution}

with

author{John Doethanks{[email protected]}}
author{Jack Smiththanks{[email protected]}}
affil{Some department, First Institution}
author{Jack Doethanks{[email protected]}}
affil{Some department, Second Institution}

and authblk will automatically handle resulting in

author{author1inst{1, 2star} and author2inst{2star} and authour3inst{2}}


renewcommand{thefootnote}{fnsymbol{footnote}}
footnotetext[1]{The two authors contributed  equally to this paper.}

This is the result.

Try this

author{
     First Authorthanks{Same Institute} and 
     Second Authorfootnotemark[1]  and 
     Third author thanks{UVW} 
}

footnotemark[1] indicating the shared footnote.