I've searched the Ubuntu Software Centre ( https://apps.ubuntu.com/cat/ ) for any "lawyer"/"attorney" - related software and unfortunately I couldn't find any. Feel free to give it a try for yourself and search this repository, maybe I missed something.
Anyway, the only solution I can think of at the moment is running a Windows emulator (such as the popular "Wine") on your Linux, and run the Windows' "Family Lawyer" type of program in that emulator, in Linux. It could work.
