I reside in nv. In a divorce case, (i am not any of the spouses) can I invoke the fifth ammendment? I am the outside person involved.

Short answer: yes.  But invoking the privilege in a civil action may not be required, and might be overcome by an appropriate extention of immunity.  For a discussion of those issues, see my newsletter discussion of a recent case here.  It is probably a good idea for you to consult with independent counsel -- prefereably a family law specialist well versed in these issues -- to avoid making mistakes.