Actually in the original trilogy the Jedi WERE cool. Their role was hinted at in the original film and then in The Empire Strikes Back we learned a lot about them through the lens of Yoda training Luke, and they were rather deeper than we had originally been led to believe. We learned about the Force and how their training really focused on being able to summon and control it while not falling prey to temptation to use it wrongly (the dark side). Then in Return of the Jedi we got to see what a fully trained Jedi Knight was actually like. And it worked very well, as Luke in RotJ is much different than Luke in either prior film - he is serious, calm, focused and perceptive.
If only Lucas had left what Kasdan wrote alone for the prequels. But instead he showed that while he directed the originals he did not actually understand what was going on in them story wise. So we got the Jedi turned into a silly monastic order who say and do incredibly stupid things, going from Qui-Gonn Dumb in The Phantom Menace through Yoda himself being portrayed as a dolt. And then there is Yoda using his baby lightsaber trying to fight people several times his size, undoing his wise sayings in Empire about the nature of the Force.
As a "devils advocate" on this (not saying I agree with it or that the prequels were my all time favorite movies or anything)
The shear size of the Jedi Order (there is like 3 levels" full Jedi-the ones we see/ Jedi staff and admin-like the librarian lady in Clone Wars/ and the Jedi security and the other "ash and trash" personnel of such a large organization. Anyone on any of the levels were supposed to be force sensitive and had been at least considered for Jedi training) with so many ppl involved, many ppl would have escaped Order 66-remember only the ppl in the temple and those on mission with their clone units were killed-maybe it was their day off? Anyhow, they were also spread out across the galaxy, we see in Clone Wars (established once again as official canon per the recent Disney "purge") how the bulky Republic/Imperial system was duped or plain out just missed things, easy for them to miss a few padawan on a field trip to an asteroid or some tech support ppl re-working some routers on an orbiting platform
. It would be very easy for a few to survive through the yrs in obscurity.
Remember we are only shown the lives and doings of a relatively small group of ppl in the movies, this galaxy is a big place, could have been many lost Jedi stories throughout the galaxy
And then there is the matter of the dismissed student of Anakin-Ahsoka Tano--the new canon also says she survives order 66 (bureaucracies; "ONLY KILL WHO IS ON THIS LIST TROOPER"). After so many Jedi are killed, would anyone be picky about someone's membership status?
AND THE BIGGEST "THING/BUT IF" Is the fact that Lucas/Disney can write in whoever or what ever they want...
just confusing that is all!
Even if he did not get married, he could have done a few one-nighters with locals and had children. They will come up with something to work with. 
In the first three films, and kind of even in the last three, the Jedi seem naive and gullible.
. The new canon is (in order):