If you can provide more context on where you found this file, I can give a much more accurate write-up. This file name is typical in several scenarios:
Used in training simulations to teach investigators how to carve files out of raw disk images or network captures. Cousins4.7z.001
Attackers sometimes split malicious payloads into numbered chunks to bypass email gateways or automated network scanners. If you can provide more context on where
copy /b Cousins4.7z.001 + Cousins4.7z.002 Cousins4.7z Linux/Mac: cat Cousins4.7z.* > Cousins4.7z 2. Extract the Contents copy /b Cousins4
Was this file part of a or a cybersecurity lab ? Do you have the subsequent files (like .002 , .003 )?
If the file fails to open, examine the raw hex data using a hex editor like HxD or the Linux xxd command.