peacefulpete, the idea that Bonobos have sometimes mated with chimpanzees (Pan troglodytes) in the modern era and produced hybrid offspring from such mating, is news to me. [Perhaps you only mean it happened long ago, instead of also in modern times.] I hadn't known such happened. After reading your claim I found an article at http://www.macroevolution.net/bonobo-chimpanzee-hybrids.html which confirms that it happened also in modern times. It says the following.
"In 1979, a circus director in France bought what he believed to be a male chimpanzee. It performed in acts and regularly mated with two female chimpanzees. This male ape, however, turned out to be a bonobo. Between 1991 and 2000, seven bonobo-chimpanzee hybrids were produced from these matings, most or all of which survived. By 2000, the oldest was working in the circus act in place of his retired father."
I notice that https://www.newscientist.com/article/2110682-chimps-and-bonobos-interbred-and-exchanged-genes/ says the following.
"Chimpanzees and their relatives bonobos are closer than we thought. Bonobos seem to have donated genes to chimps at least twice in the roughly two million years since they last shared an ancestor.
The two closely related apes have occasionally interbred in captivity, and bonobos are renowned for their free and easy sex life. But the finding that they interbred in the wild was unexpected."