\documentclass{article}
\usepackage[en-US]{datetime2}
\usepackage[date=en-US,abbrevparents]{nehgs-register}

\definepersonkv{alex-example}{
  name        = {Alex Example},
  preferred   = {Alex},
  parents     = {},
  index       = {Example!Alex},
  birth       = {1950-01-12},
  birth-place = {Boston, Massachusetts}
}

\definepersonkv{jordan-sample}{
  name        = {Jordan Sample},
  preferred   = {Jordan},
  parents     = {},
  index       = {Sample!Jordan},
  birth       = {1952-05-04},
  birth-place = {Providence, Rhode Island}
}

\definepersonkv{casey-example}{
  name        = {Casey Example},
  preferred   = {Casey},
  parents     = {alex-example,jordan-sample},
  index       = {Example!Casey},
  birth       = {1979-12-16},
  birth-place = {Dayton, Ohio}
}

\begin{document}
\section*{Minimal Register Example}

\begin{registersection}
\mainperson{alex-example} was born in \getpersonbirthplace{alex-example} on \getpersonbirthdate{alex-example}.

The child of Alex Example and Jordan Sample is:
\begin{childrenof}{alex-example}{jordan-sample}
  \childref{casey-example}{b.~\getpersonbirthdate{casey-example}, \getpersonbirthplace{casey-example}.}
\end{childrenof}

\mainperson{casey-example} was born in \getpersonbirthplace{casey-example} on \getpersonbirthdate{casey-example}.
\end{registersection}

\checkregister
\end{document}