The "1914 Generation", as taught by the Society in the 1960's & early 1970's, were thought of as those associated with the WT Society who were then already in their midteens or older when Christ took the throne invisibly in 1914 as only they could "understand" the importance of & witness these "signs" & "events" which signaled this "invisible presence". Note that this "Generation Doctrine" was already a highly modified and reworked belief by the time the Society started pushing the 1975 thing in the '60s. The fact that these Bible Students (pre-JW name) in 1914 had no clue that this invisible Christ's presence doctrine even existed is enough to show what nonsense this belief was in of itself. In any case, this was taught as it meshed well with the whole "Creative Day" of 7000 years of which the last 1000 years would be the sabboth in which Christ would reign over the New System. In order to get to this last 1000 years the first 6000 years since Ol' Jehover's last creative act (Eve) was calculated using traditional Jewish & Catholic chronologies as coming to an end in the mid 1970's. By the mid 1970's even the youngest of this "1914 Generation" would be around 75 years old giving the Society a very mature biblical generation who would be dying off. Since that Generation would not pass away before the big "A" this had to be right. Are you confused yet?
In any case, nothing happened in the mid 70's and now this "Generation"'s youngest members would be 105 years old by now. It is easy to see why the Society started bringing down the age of " understanding" to 10 year olds and then no "understanding" was needed so babies could be used to stretch out the troublesome time lag. Hence the playing down of the literal die off of that "Generation" in 1995 to include everyone born since effectively making a generation concept useless since it has no limits. Even if babies born in 1914 were used they are now 91 years old if still alive. The reality of how silly this all is becomes even more clear when true use of the word generation is applied to the people of any given time. For instance the WWII or the 1960's generations are not thought of as children & babies but rather of the movers and shakers of society in that time. These influential people generally range from their mid twenties to forty year olds and this is understood by everyone but JWs. In 1914 30 years old is a nice round number for an average generation age and using this age gives us people who would now be 121 years old. Let's get real, that generation is long gone. Most of them were gone before 1960. Only a true fanatic could still believe that any of this really means anything.