Not even one of them will break the seal.
Vicki Dunne, the second member, pointed out that a priest who breaks the seal of confession incurs an excommunication that can be lifted only by the pope. In addition, it would undermine Catholics’ trust in the "sacred, sacramental and sacrosanct" rite.
No one mentions that breaking a vow is a mortal sin.
Sin is so rarely talked about these days. Perhaps if sin (and its wages) were talked about there would less of this sort of thing going on.