That's called amplexus, a mating behavior where the male mounts the female and induces her to release eggs for him to fertilize. It's possible you have two male frogs who have been mounting each other. read more
African dwarf frogs don't have an ounce of aggression in their tiny bodies. Even two males can live together peacefully. Your frogs might seem aggressive toward each other, but that's typically either because they're crawling over one another or they're attempting to mate. When mating, they sometimes look as if they're hugging one another. read more