Why did Roman emperors mostly adopt, while European monarchs were obsessed with bloodlines?

The Annaeus family from which the Senecas came is likely to have been the result of such an intermarriage: the name Annaeus seems to be non-Roman. 8 Compromise between diverse social groups was thus an essential habit in the Annaeus family background.

The Roman senate gradually became what we might now describe as a decidedly multicultural body, and the full list of Roman emperors contains many whose origins lay outside Italy:

Towards a new history – of emperors

‘Good emperors’ and ‘bad emperors’?

Another problem that dogged the history of the fourteen emperors over the first two centuries CE, and one that preoccupied ancient writers above anything else, was the relationship between the men on the throne and the senators, and the question of how the senate was to operate under an autocracy.