You will need an extra field, a calculation. Set the calculation to:
That will get the last word regardless of how many lastnames they have and you can sort on that.
That looks like that would work. I do not want to have to set up a whole nother field, so I think I will have to put the first name in her last name as a second name in her first name, if that makes sense (Debby Smith will be her first name and Jones will be her last name. Too bad there is not a key combination that just tells FMP to skip over that name when sorting, like there was in AppleWorks.
Thanks for the help!