You do realize that all of the genetic material used in DNA testing of this type is CONSUMED in the process and nothing is left but some 1 and 0’s in a computer for 13 genetic markers. There is nothing left to synthesize.
Unfortunately you are way off on this tin foil hat theory. Even if the police have Familial DNA, they would still be required to obtain an original DNA sample from the suspect before an arrest warrant would get issued. If you know who your suspect is, familial DNA will NOT benefit you in anyway. The only use for familial DNA would be if you DIDNOT know who your perpatrator was and a father or brother (or sister or mother) of the suspect had previously had a sample submitted. If you know your suspect and CANNOT get probable cause (which is a very unlikely scenario,since establishing PC for a DNA swab warrant wouldn’t take much) OR you don’t want to tip off your suspect, then a covert DNA sample would be needed anyhow.