Here’s what’s happening on Page 156:
Pip, Handel according to Herbert, finds out that Miss Havisham’s half-brother was in on the cruel scheme with her fiancé to swindle her out of her fortune. (Poor Miss H!) Herbert does not know where the two men are today. They seem to have disappeared. Estella was adopted by Miss H at some point – also something Herbert knows little about. Maybe we will find out later.
In the meantime, Pip and Herbert agree that they both now know the exact same information about Miss H.
How horrible to be ready for the wedding, in the gown, cake on the table, only to find out that it was all a cruel joke, a mean scheme!