Surah 29:27
And We bestowed on him Isaac and Jacob, and We established the prophethood and the Scripture among his seed, and We gave him his reward in the world, and lo! in the Hereafter he verily is among the righteous.

According to this scripture, the prophethood was established with the seed of Isaac and Jacob. How come allah's messenger regards himself as one of the prophets when we know that he is a decendant of ishmael. Surely, by this ayat, allah's messenger is not among the prophets seeing he is not of the lineage of Isaac and Jacob.