I’m no expert, but here are what I find to be the relevant canons:
**Can. 983 **§1. The sacramental seal is inviolable; therefore it is absolutely forbidden for a confessor to betray in any way a penitent in words or in any manner and for any reason.
§2. The interpreter, if there is one, and all others who in any way have knowledge of sins from confession are also obliged to observe secrecy.
Can. 1388 §1. A confessor who directly violates the sacramental seal incurs a latae sententiae excommunication reserved to the Apostolic See; one who does so only indirectly is to be punished according to the gravity of the delict. §2. An interpreter and the others mentioned in ⇒ can. 983, §2 who violate the secret are to be punished with a just penalty, not excluding excommunication.
So that answers your second question. Unfortunately, I don’t see any specification of when the seal begins. Brendan’s explanation seems legitimate, though (that his father may have already made the information public).