Tarkasur had a boon by Lord Shiva that he could be killed only by Shiva's son. Devtas assigned Kamadeva to stop Lord Shiva's meditation and create love in his heart, so that as a result Shiva's son can be born.
Kamadeva and Rati were played their role to create love between Lord Shiva & Parvati, but when Lord Shiva come to know about this, he got angry and opened his third eye. A fire raised from his third eye which burned the Kamadev.
On request of Kamadeva's wife Rati, Lord Shiva gave her a boon that in Dvapara Yuga, Kamadeva will re-born as Shree Krishna's son named Pradyumnna.
Now without the Kamadeva, it is not possible for a new life to born. So the question is How the new life was being created between the time period of the death and the re-born of kamadeva?