Police are seeking public assistance to help locate missing siblings Daniel Jansse and Lalita Ditmar-Jansse.
Daniel and Lalita, aged 16 and 13, were last seen at their South Clarinda address about 10pm on Monday, 2 November.
It is believed they could be travelling on public transport in the Chelsea and Frankston area.
Police and family hold concerns for the pair due to their age and their disappearance is out of character.
Investigators have released an image of Daniel and Lalita in the hope someone recognises them and can provide information regarding their current whereabouts.
Anyone with information about the pair is asked to contact Moorabbin Police Station on 9556 6565.