The Prophet of Allah, sallallaahu 'alayhi wa sallam, would seek his relatives’ help in important matters:
In the story of the Pledge of 'Aqabah that was narrated by Ka'b ibn Maalik (a Companion) he said: "We left for pilgrimage, and the Prophet of Allah, sallallaahu 'alayhi wa sallam, promised to meet us at 'Aqabah in the middle of the days of Tashreeq (11, 12 and 13 of the month of Thul-Hijjah). So we gathered in that place waiting for the Prophet of Allah, sallallaahu 'alayhi wa sallam, until he came to us with his uncle Al-'Abbaas, who had not yet become Muslim, but he wanted to attend to the affairs of his nephew and make sure he would be safe.
When we sat down Al-'Abbaas was the first to speak, and he said: "O Khazraj (from the Ansaar), Muhammad is from us, as you know. We have protected him from our people and he is well protected and honored in his land. But he insisted to come to you and join you, so if you think that you will fulfill what you invited him for, and can protect him from his opponents, then you can have that. But if you think that you will turn him over and not support him after he comes to you, then leave him right now, for he is well protected from his people." The Ansaar said: "We have heard what you said: so speak, O Prophet of Allah, and take what pleases you and your Lord." So he, sallallaahu 'alayhi wa sallam, spoke, and read the Quran, and called to Allah, and enjoined the people to become Muslim..."