slight problem with Quatre Mains

[Thorkil Wolvendans]

Hi group!

Lily allows us to engrave music for two pianos, correct? I believe I did 
everything correct to make lily print two piano staves, but instead of 
showing 2 piano staves, it only shows piano staff 2. I must have made a 
silly mistake, but I can't find it.
Could someone be so kind as to look at my thingy, and tell me what I did wrong?
Thank you in advance!

Avé,
Thorkil



===my input===

\version "2.2.0"

\include "nederlands.ly"

%%% PIANO I %%%
timei = \notes {
        \set Score.barAlways = ##t
        \set Score.defaultBarType = ":|:"
  \time 4/16
}

upi = \notes \relative c'' {
\clef "G_8"
  c4
}

lowi = \notes \relative c {
\clef bass
  c4
}

%%% PIANO II %%%
timeii = \notes {
        \set Score.barAlways = ##t
        \set Score.defaultBarType = ":|:"
  \time 4/16
}

upii = \notes \relative c'' {
\clef "G^8"
   c4
}

lowii = \notes \relative c {
\clef bass
  c4
}

\score {
\context StaffGroup = pianos <<
  \context PianoStaff <<
      \set PianoStaff.instrument = "Piano I  "
    \context Staff = upper \upi \timei
    \context Staff = lower \lowi \timei
  >>
  \context PianoStaff <<
      \set PianoStaff.instrument = "Piano II  "
    \context Staff = upper \upii \timeii
    \context Staff = lower \lowii \timeii
  >>
>>

 \paper {
   raggedright = ##t
  \context {
   \ScoreContext
   \remove "Timing_engraver"
  }
  \context {
   \StaffContext
   \consists "Timing_engraver"
  }
 }
}
===end of my input ===