Cass could understand, more than understand, Harry's need not to keep secrets any more. He'd kept enough of them in his life and he knew the burden they could be.
'I'll tell you both soon, I promise,' he said. 'I know it's not fair to ask you to keep things from each other, but it's just for a little while.'
He would tell Harry before he moved in with Percy, and he'd tell Pansy as soon as things were a bit more settled. She deserved to know, they both did.