[1][2] The only information existing about the lives of Ertuğrul's elder brothers is about what they did before the division of the Kayı tribe.

Sungurtekin (Ottoman Turkish: سنقوردكن) worked as a spy for the Seljuks in Ögedai's army and passed on the information he got but was possibly killed when he was caught.

The reason why Ertuğrul and Dündar decided to migrate to Söğüt was either that they wanted to escape the Mongol onslaught, what the Turkmen tribes had been doing for decades, or that they wanted to populate the area gifted to Ertuğrul by Keykubad I with Oghuz Turks.

In Turkmenistan, the Kayı tribe is one of the main divisions of the Geklen Turkmens living in the Balkan Region and consists of the following clans: adnakel, ak kel, alatelpek, bagly, barak, burkaz, ganjyk, gapan, garabalkan, garawul, garagol, garagul, garadaşly, garakel, garga, garyşmaz and others.

[4][5] In Diriliş: Ertuğrul, Gündoğdu Bey was portrayed by the Turkish actor Kaan Taşaner.