Could the OP explain what is meant?
First guess: reference to the 10 Commandments. "I the LORD thy God am a jealous God, visiting the iniquity of the fathers upon the children unto the third and fourth generation of them that hate me,"
thus the fifth generation starts anew...Vulgate has quarta generatio...so you would want quinta generatio.
Second guess: computer languages? Let's see...1st generation was machine language, 2nd generation was assembler, 3rd generation was Fortran/C/Basic, 4th generation: Gauss, R, S+,...
5th generation: something derived from Gauss, R, S+?
Third guess:
You actually are 5th generation? "I'm a 5th generation American?"