This is a popular adult visual novel (AVN) developed by virtual_indecency . It features first-person storytelling and choices that impact the narrative. A walkthrough for these chapters is often sought out due to the branching paths.
Sister, Sister, Sister: Chapter 2 by virtual_indecency - itch.io This is a popular adult visual novel (AVN)
Searching for "Sister Sister" on sites like Socigames often leads to a few different titles, most commonly referring to adult visual novels or indie horror games. Depending on what you are looking for, Most Likely Games Most Likely Games