Translation:My newspapers were taken by my nephew.
"A third person agent can be expressed by either dia or -nya. They are optionally preceded by oleh 'by'.
Saya dijemput dia/oleh dia.
'I was met by him'
Oleh is always optional except when the agent does not immediately follow the verb, in which case it is obligatory. This occurs when another clause element comes between the verb and agent or when the agent is placed before the verb to receive highlighting. " Sneddon, J. N., Indonesian, a comprehensive grammar, p.248