Legal Question in Civil Rights Law in California

Regardless of whether the suit is frivolous or not, you will need to defend yourself. Default judgments can be entered on frivolous suits.

The plaintiff's father can indeed act as a process server.

Without seeing the paperwork being mailed, it is not possible to tell you whether service has occurred or not. The controlling authority is Rule 4 of the Federal Rules of Civil Procedure.

I strongly suggest you meet with an attorney to advise you as to how to best defend yourself. It may be that you can do it "in pro per," but in this case you really should hire a lawyer on at least a "limited representation" basis to guide you.