Mukuro can sympathise. It sure is awkward when your sibling is involved in kicking off The Biggest Most Awful Most Tragic Event in Human History tragic and world ending consequences, huh? She won't go into detail but will at least tell him that much about her sister.

The Pierrot though...that warrants further research.

She'd want to know if there's anything he'd want them to do- or anyway she can help him find peace. (And once again wander why she of all people was picked to save her world. She's glad she has Jean's moral support!)