Samina and Mirza, from Gilgit-Baltistan’s Shimshal Valley, scaled the 4,884-metre high Carstensz Pyramid, also known as Puncak Jaya, after a six-hour-long climb and hoisted the Pakistani flag on its top in the early morning of Wednesday.
The peak is fourth of the seven summits the siblings will be climbing in the expedition dedicated to promote gender equality, youth development and women empowerment.
The duo is a part of the Adventure Diplomacy Group , set up to support their campaign.
The group consists of the Serena chain of hotels and the embassies of USA, Russia, Argentina, Indonesia and Nepal.
“We are so thankful to have made it to the top today after six hours of hard climbing. It feels really great to be here”, Samina was quoted as saying on telephone by the Adventure Diplomacy Group.
At the completion of their seven summits campaign, they will become the only siblings in the world to have achieved such a mountaineering challenge together.
In December 2013, the pair climbed Mt Aconcagua in Argentina, the highest peak in South America.
In January, they scaled Mt Vinson, the highest peak in Antarctica, and then in February they climbed the 5,895-metre-high Mount Kilimanjaro in Tanzania.
The siblings will be attempting at scaling the 6,168 metres high Mt McKinley in Alaska and the 5,642 metres high Elbrus Peak in Europe in August 2014.
Samina Baig rose to prominence by becoming the first Pakistani woman to climb the Mount Everest on May 19, 2013.