\documentclass{article}
\usepackage{pgfkeys}
\usepackage{pgfkeyx}
\makeatletter

\begingroup
\def\iden#1{#1}
\catcode`\/=13
\catcode`\,=13
\catcode`\==13
\iden{\endgroup
  \pgfkeys{%
    / my family / .is family,
    /my family/my keys/.cd,
    keya / .code = \def\keyavalue{#1},
    keya/.default = {keya-default},
    keyb / .code = \def\myvalueb{#1},
    keyb /.default=keyb-default,
    .normal code=\def\x#1{#1},
    keyc/.code=\pgfqkeysalso\pgfkeyscurrentpath{#1},
    keyc/.value required,
    keyd/.is if with no callback = true,
    keye/.is if with 1 callback = {true}{\def\x##1{##1-True-#1}},
    keyf/.is if with 2 callbacks =
      {true}{\def\x##1{##1-True-#1}}{\def\x##1{##1-False-#1}},
  }%
}

\pgfkeys{%
  /my family/my keys/.cd,
  keya={x},
  keyb=aa,
  keyc = {keya=aa, keyb=bb},
}

\pgfkeys{%
  /my family/my keys/.cd,
  keya/.restore default,
  .restore key defaults={keya,keyb}
}

\makeatother

\begin{document}
\pgfkeys{%
  /my family/my keys/keyf=true,
}
\ifkeyf
  \texttt{`keyf'} is \textsf{true}.
\fi
%\show\x
\end{document}
