Did Ibn Umar sit down to urinate in the places where he saw the Messenger of Allah urinate?

Perhaps the questioner is asking about Ibn 'Umar, may Allah be pleased with both of them, emulating the Prophet's natural actions. This is indeed established about Ibn 'Umar, may Allah be pleased with him, that he would dismount wherever the Messenger of Allah, peace be upon him, dismounted, and he would pray wherever he prayed, and urinate wherever he urinated, and sleep wherever he slept. It is well-known that Ibn 'Umar was unique among the Companions, may Allah be pleased with them, in this regard. The actions of the Prophet, peace be upon him, include those that are purely legislative, and those that are purely natural and not considered legislative, yet there is no harm in emulating him in them.