There is an indirect connection between the works of Lenard and the Curies. This link is exactly the work of Röntgen and the influence it had. Let me expand on this a bit.
Lenard was unhappy that the public attributed the discovery of X-rays entirely to Röntgen. He believed that he should also be acknowledged, because Röntgen's discoveries were made by Crookes–Hittorf tube and Lenard tubes. After the war, during an interview made by an American colonel, V. Etter (who was a medical doctor, and would later a professor of radiology), Lenard said the following:
"I am the mother of X-rays, Just as the mid-wife is not responsible for the mechanism of birth, so was Röntgen not responsible for the discovery of X-rays since all the groundwork had been prepared by me. Without me, the name of Röntgen would be unknown today."
(See, Etter, L. E. (1946) Some historical data relating to the discovery of the Roentgen rays. Am. J. Roent. Radium Ther. 56,220-231.)
The discovery of X-rays directly influenced the research of Becquerel and the Curies. Indeed, Becquerel was in the audience, when Poincaré (after getting a letter from Röntgen) gave an enthusiastic talk in 1896 at the Académie des Sciences in Paris about the discoveries of X-rays. Influenced by this talk, Becquerel wondered whether there was any connection between the X-ray images on photographic plates and the phenomena of fluorescence and phosphorescence that he was studying. The rest we know: He designed an experiment. He was exposing fluorescing material to the sun, and then placing it and a metal object over an unexposed photographic plate. This didn't really work. However, while doing this experiment during a rainy day, he wrapped a fluorescing uranium compound (potassium uranyl sulfate) in a black cloth along with a photographic plate and a copper Maltese cross - and put it in a drawer. Several days later, when removing the plate from the drawer, he discovered to his surprise that a distinct image of the cross appeared on the plate (despite it had never been exposed to sunlight). The image resembled Röntgen's X-ray images, and the radiation seemed to have the penetrating power of X-rays. The enthusiastic Becquerel wanted to know whether this was X-ray (turned out not to be), and which other materials could emit such radiation. His young student, Marie Sklodowska Curie decided to look into these "uranium rays" as a possible field of research for a thesis. And there followed a period of intense research into radioactivity by her and her husband Pierre Curie.
Thus, there was a clear line of influence Röntgen-Becquerel-the Curies with superb research results (with all of these people acknowledging each other). Lenard believed that he should be in this line, as his results directly influenced Röntgen.
(Personal note: Lenard was acknowledged and was regarded as a great scientist, but his ego couldn't tolerate that others, like Röntgen and the Curies, got even more fame.)