My sister had graduated that year, and I attended the commencement ceremony. And she had talked about Visigoths and things like that that she had spoken about in her commencement speech. And essentially she was speaking up for the teachers and the biology textbook.
Their sister did not speak at their own commencement ceremony. 
( z1 speak :polarity - :ARG0 ( z2 person :ARG0-of ( z3 have-rel-role :ARG1 ( z4 they ) :ARG2 ( z5 sister ) ) ) :location ( z6 ceremony :mod ( z7 graduate ) :poss z4 ) )