They may have been asked to attend by the Italian court or by the prosecution? Or perhaps even by the defense.
I suspect pawns, more than anything else. While you would expect the family of a victim to be "out for blood", and perhaps understandably less concerned that it's the
right blood, in practice this seems to be relatively rare; most of the families seem to understand that it's important to get the right guy, they object when their plight is misused to further injustice, and relatively few families of murder victims express a desire to see the perpetrator executed. Most people have internalized the message that vengeance won't make them feel better. (Which is too bad, because the emerging research is that vengeance actually
does make you feel better, a lot better; it's just that what the government does isn't vengeance, so criminal punishment doesn't seem to have that effect.)