It is important to clarify that the string of text you provided ( ssis787 eng sub my abhorrent fatherinlaw108 better ) does not correspond to a known, legitimate film, television series, or published literary work as of my latest knowledge update.
The formatting strongly resembles the naming conventions used on unauthorized file-sharing or piracy websites, where numbers like "787" or "108" often refer to encoding releases (e.g., "1080p") or arbitrary file identifiers. Additionally, "SSIS" is a known production code prefix for a Japanese adult video (AV) studio (S1 No. 1 Style). Combining "SSIS" with familial relationship terms ("father-in-law") strongly suggests content that is produced, scripted, and performed by adult actors, often within specific exploitative or taboo genres.