Not related and not researching the above mentioned surname. I have some websites that might help you in your search.
www.rat.de/kuijsten/navigator www.genealogy.ro www.whitepages.ro Romania's phone site is listing PORUMBESCU in city of Bucaresti. The only city I looked. www.google.comgives out websites on Ciprian Porumbescu. You might have to hire a researcher in Romania. Is Sibot the place of your great grandfather?