Mary and Bill Sutton had two children, Margaret and Russell. Bill is now working at the Warwick homestead; his wife left him because he was an abusive addict; he hit Margaret and sold their brahmin. The rest of the family settled at Taffington Boathouse. Margaret and Russel found an old holotape that would lead them to a pre-war stash of chems, which they planned to trade for a new brahmin; unfortunately, they disturbed a nest of bloodbugs and all three were killed.
Russell found the holotape and it can be found on his body. It says:
Greetings Brothers. You are here because it is that time of year when we induct our newest members into this most esteemed fraternity. Before their initiation is complete, they must be prepared to receive the mysteries of our order. You can find the substances necessary to open their minds in the drainage, as you all remember from your own initiation. Remember, that the pledges should be blindfolded before you bring them up the canal, and keep an eye out for anyone out late in the park. The elders will be by Sunday evening for dinner, and all new pledges must be present, so stick to the normal dosage. Ordo Oblitus Ossa!
Presumably, Taffington Boathouse was a fraternity (or was just used for initiations.) He left Margret a note telling her to cover for him:
Margie,
I snuck out last night and had a look at the drainage pipe at the end of the canal. It's cracked and it looks like if I clear away some of the garbage, I should be able to get in. I think it's the opening they mentioned in that holotape. If we can get those chems, we might be able to buy a new brahmin.
I'm gonna check it out, but I told mom I was going over to the Slog to trade for some tools, so cover for me. I should be back by evening.
- Russell
When a day passed and Russel didn’t return, Margaret went to look for him, leaving a note to explain things to her mother:
Mom,
Russell has been gone over a day now and I'm getting worried. We were going to wait to tell you, but we found an old holotape from before the war in the boat shed. It sounded like someone had stashed some chems in the drainage at the end of the canal. Russell thought we might be able to sell them to one of the traders. Maybe use the caps to buy another Brahmin.
I'm sorry we didn't tell you, we just wanted it to be a surprise. But that's the second one of those bugs we've seen today and I think something went wrong, so I'm going to have a look for him. Don't worry - I'm just going to take a quick peek and I'll be back soon.
-Margie
Bill Sutton is unaware of his family’s death and he can’t be informed of it. He has a note in his inventory from his (ex) wife, and in a random event, Bill will jump into the water and kill himself. You can stop his death by having him put on Acrobat armor so he doesn’t take fall damage or by stealing the note.
Bill,
It's over.
I mean it this time. You aren't the man I married anymore. That Bill wouldn't have sold our brahmin for chems. You're a mean, abusive drunk and we're done. Margie still can't see clearly in her right eye. Just stop and think about that. You may have blinded your own daughter. The kids and I are leaving and if you even think of coming after us, Russell has already said he'll kill you if he ever sees you again, and I've half a mind to let him.
- Mary
(The pictures are from the Fallout wiki. All but Bill’s photo were taken by respawning the characters using console commands.)