At least of the early period. It seems like very few emperors had any luck siring biological children, even though they very much did try. Pregnancies seem to have been few and far between, even though many emperors were married to multiple women in succession, with a great number of stillbirths and miscarriages.
One professor of mine believed that it was because of the large amount of lead that the wealthy Roman unwittingly had in their diet, particularly from the consumption of wine, as wine was sweetened with grapes boiled in a lead pot. The toxic element contributed to a plethora of health problems, infertility being only one of many.
I am very curious, what do others think of this subject?
Welshhoppo t1_iyewt20 wrote
So it's less a case of having children. Which a lot of Emperors did have. It was a case of having children survive to adulthood in a political world where murdering your enemy was a viable tactic for getting ahead. Augustus had his daughter Julia, who gave him loads of grandchildren, in fact she seemed to have problems not being pregnant. Tiberius also had a son, who died due to interference from the Praetorian Prefect Sejanus. Caligula, his successor, had a daughter who was murdered. Claudius had four and all of them were murdered. And Nero also had a daughter, who died in early childhood.
So it was a very hard environment for children to actually survive. Especially when blood relation to the ruling Emperor and Augustus was very important for maintaining power. But you had the low survival rates combined with the seemingly deadly game of politics combined with various other dangers that come from ruling a state, such as death in warfare or on campaign. It's one of the reasons why adoption was seen as being as legitimate as being blood related, because sometimes you just have bad luck.