\indvdldef{youngSybil}{Lady Sybil}
\indvdldef{youngEdith}{Lady Edith}
\indvdldef{youngMary}{Lady Mary}
\sblngdef{youngSis}{youngMary,youngEdith,youngSybil}

\indvdldef{Robert}{Robert Crawley}[7th Earl of Grantham,\maleline]
\indvdldef{Rosamund}{Rosamund Painswick}
\sblngdef{RobertRosamund}{Robert,Rosamund}

\gensdef{family}{RobertRosamund}{
  {Robert}{youngSis}
}
\fbox{\usebox{\family}}