I do have a question regarding the Green-card filing of my parents. I am going through USCIS website here: https://www.uscis.gov/sites/default/files/files/form/i-130instr.pdf
Now, if I understood correctly, IF I am filing for my sister, for example, I am going to file for her and when she receives her green card, her husband and 5 years old kid would get it with her because they are her immediate family.
What I am failing to understand here is that IF my sister's husband is considered her family so that he can immigrate with her, why can't the same logic apply when it comes to my parents. That being I only apply for either of my parents and then since the other parent is an immediate family of parent1, they receive the green-card automatically?
I am just confused and curious. Any suggestions?