Yes, there is a history there.
The Rita who returned in January 1972 was a totally different character from the exotic dancer from 1964. It was only because Barbara Mullaney played both parts that they became one and the same later on. Mrs Bates, as she was then known, had a husband and two children, and was set up as a bit of a harridan before we met her. At that time, Ken was Bessie Street School's deputy head, and taught her son Terry Bates. Ken had taken Terry under his wing, and believed that his schoolwork was being affected by him having to look after his younger sister while his mother worked (the horror!). Ken visited Rita to see what he was up against, and they ended up hitting it off. They kept in contact, at first by letters, and later by meeting socially, with the pretext of discussing Terry (Rita was portrayed as a bit of an unfit mother). It didn't lead anywhere though, as Rita took up with Len a few weeks later.
They arranged another date in September 1973, when Rita was fully established. Both Ken and Rita had recently suffered heartbreaks and it was very much a rebound thing, but Ken stood Rita up when Albert Tatlock guilt tripped him into visiting Peter and Susan in Glasgow instead of chasing women.