Translation:They are the siblings of the engineer.
I don't think so. Μηχανικός originates from the ancient Greek μηχανή (machine), which is also where the english word mechanic comes from.
As for the turkish mühendis, according to wiki, it comes from the arabic muhandis, which originates from the Persian andāza or Middle Persian handāza. https://en.wiktionary.org/wiki/m%C3%BChendis
So as you can see, the origins of the two words are actually different. ^.^
I initially translated the whole sentence as "They are his siblings' mechanic."
Whenever I hear
του after a noun, I think
τα αδέλφια του =
his siblings. Are there any tricks to not confuse
του with the Genitive Definite Article and "his" ? Dumb question sorry. I get confused in this scenerio whenever it appears.