I understand that there hadn't been primogeniture, and the desire for a male child wasn't the same as, say, medieval Europe, but Augustus was the wealthiest person in Rome, and lacked good male heirs after the deaths of Marcellus and his grandchildren. Did he try to have additional children, but could not? Certainly Livia was capable of bearing children (Drusus, Tiberius)
Augustus(Octavian at the time of this event) and Livia did attempt to have children after their marriage. Both had children through separate souses, as you mentioned Tiberius and Drusus from Livia and Julia from Octavian. Livia was actually pregnant at the time of her marriage to Octavian, prompting a saying that the lucky Livia could give birth only two months after marriage. After the birth of Drusus, Octavian got Livia pregnant for a third a final time. Unfortunately for the newlyweds the pregnancy ended in a miscarriage and Livia would never become pregnant again. Whether this was because of damage to the uterus from the pregnancy or from a possible STD picked up from Octavain’s frequent womanizing is unknown because of the limits of ancient medicine and source material. Despite this, the two remained married for the rest of Octavian’s life and he had to look elsewhere for his future heir. As a result of his long reign, many potential heirs died before their adopted father, eventually, Tiberius would ascend to the position of Princeps.