I haven't had to deal with FAFSA yet. Are we talking a really simple one-page form saying "I can't pay for my kids, here's my SSN so you can verify for yourself, signature", or are we talking pulling together years of tax returns and bank statements and other financial data? If it's the latter, I can absolutely see exhausted parents who don't see the value of college not wanting to expend the effort.

Which doesn't invalidate the other things LW says that indicate a general pattern of parental neglect once the kid is no longer an adorable baby. And if LW's parents want to see their grandkids, they should be making at least as much effort as LW is.