Replaying Chapter 3 only did not work for me since I must have picked more positive decisions to strengthen their bond in the previous chapters. This is solely to help point out the decisions I made overall in all chapters to accomplish a more negative outcome for the Life Tears Us Apart achievement. Performing the opposite actions should net you Twins4life.
I did the Replay option from the beginning of Chapter 1 and restarted my progress. Hold
to skip all cutscenes to make this go much faster. I also skipped most memory sequences if they weren't required to progress the story. This shouldn't take you more than 2-4 hours at most, depending on where you decide to start.
Chapter 1- Don't accept Eddy's gift from Alyson on the boat.
- Break open Mary-Ann's door in the Ronan house. Don't solve the puzzle.
- Choose Alyson's memory in the grocery store "Tessa was angry".
- Pick the option "Eddy did his best for me" at the Police Station.
At the summary screen I received "disappointed", "downhearted", "lack of trust", and "rift". The star was also split in half after those four scenarios.
Chapter 2- Choose Alyson's memory "Mary-Ann was sad".
- Pick the option "Let's do it" when speaking with the realtor on the phone.
- Pick the option "Are you kidding me?!" when confronted by Eddy after the Archives section in the Police Station.
- Pick the option "Even after what I did for you?" at the dock.
At the summary screen I received "discarded", "didn't feel heard", and "felt let down". The star was still split in half after those three scenarios.
Chapter 3- Tell Michael about the memories, then pick the option "Won't do any good".
- Pick the options "We're too different" and "I was the kid who killed his mom" during the ice fishing conversation with Michael.
- In the loft, break open the small chest with the crowbar instead of cracking the code. Then pick the dialogue options to proceed with breaking it open.
- Choose Stick to your memory "Mary-Ann threatened Tyler" but I do not think this decision is pivotal to the final outcome. I believe this is what gives you the different epilogues, and the opportunity to do the Tyler/Alyson endings regardless of their bond.
At the summary screen I received "disappointed", and "the twins' bond was broken". Achievement unlocked during the credits.