Robin has been around since almost the beginning of Batman's comic career. A year after Batman's debut in Detective Comics, Robin was brought on to attract young readers, and he was immediately a hit. While Dick Grayson eventually grew up and attended college, where he had the occasional girlfriend, Bruce for the most part was always married to his crime-fighting and showed the opposite sex very little attention (except for Catwoman, who is pretty much Gotham City's answer to Lady Gaga). Most of the "evidence" for Batman and Robin's hidden homosexual lifestyle come from comic panels that at the time seemed acceptable, but have since been regarded as gay or pedophilic in nature. In fact it was the Dynamic Duo's "relationship" that sparked comic controversy back in the 1950s, when parents and politicians felt comic books to be evil and responsible for the teenage rebellion of that day.
The gays have always loved Batman and Robin (remember Chris O'Donnell's bat-nipples in Batman and Robin?) and the most recent controversy arose when artist Mark Chamberlain debuted his watercolor collection in New York in 2005 that depicted Batman and Robin in various sexual positions and acts together (you can Google Image search them yourself). The art gallery was hit with a cease and desist order by DC Comics to hand over all unsold work and invoices for the sold pieces. Like being the Oprah and Gayle of the comic world, most evidence points to Batman and Robin just being best friends, but one gay can dream about what latest "Bat-gadgets" Bruce and Dick are trying out in the late hours of the Batcave after a long night of cleaning up the streets of Gotham.