This is the clearest statement by an accepted authority, that explains current beliefs that I have found to date.
The fundamental particles
http://www.physics.usyd.edu.au/hienergy/probing_structure.html
Three and only three?
It is not yet known why there should be successive "families" or "generations" of fundamental particles in this way. The fact that both the leptons and the quarks are laid out in a repeating structure, suggests to some that these particles may themselves be composite, made up of yet smaller entities the way that nuclei are made up of protons and neutrons, while protons and neutrons are made up of quarks.
To date there is no evidence for this. A 1996 suggestion of quark structure by the CDF collaboration, discoverers of the top quark, has more recently appeared to be something more prosaic.
There do seem to be only three generations
I am sorry I cannot be more helpful as this is my speciality, but amatuer theories are not permitted on this PF. My work has been debated by two colleges of higher education, one scientific debating group and I once received a correction from a leading astrophysicist who's work I had quoted; but I cannot get it peer reviewed. These are problems all researchers have to face, but the struggle is its own reward.
Enjoy your research
elas