I know a Muslim who does not know how to pray his parents never taught him. He is religious and tries to be the best Muslim he can. Is this person considered a Muslim or does he just have the name even though he does everything in the 5 rules of Islam other than pray?

Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

First, know that we cannot describe somebody as truly religious until he establishes the Divine obligations, and performing prayers is the most important Divine obligation after belief in Allah.
No doubt that performing prayers is the most important pillar of Islam and its basic criteria. Then, we cannot say that so and so is religious as long as he does not perform prayers.
The said person has to repent to Allah instantly and faithfully, and then to perform his prayers in their fixed times with Muslims.
Then, he has to learn what is essential for every Muslim, i.e. at first what is related to one's creed and worship.
Also, his parents' negligence to teach him does not give a legal justification as long as he become pubescent, and no doubt that his parents will be questioned for their negligence.
As for your duty towards this person, you have to do your best to teach him prayers: importance and performance. And you are to remind him of Allah's statement in al-Qur'an and His Prophet (Sallallahu Alaihi wa Sallam)'s Hadith {Guard strictly (five obligatory) AsSalawât (the prayers) especially the middle Salât (i.e. the best prayer 'Asr). And stand before Allâh with obedience [and do not speak to others during the Salât (prayers)].} [2:238]
The Prophet (Sallallahu Alaihi wa Sallam) said replying for a question: "The best action is to perform prayers at their fixed times." [ Bukhari and Muslim ]
You have also to clarify to him that prayer constitutes the dividing line between a Muslim and a non-Muslim. The Prophet (Sallallahu Alaihi wa Sallam) said: "Between a person and polytheism and disbelief is discarding prayer."
As for one who does not perform prayers without denial of its being an obligation, there is disagreement among scholars in this concern, i.e. if one becomes a true disbeliever or not. Each group has its own evidence. Anyway, the said person has to repent, to learn his religion and to put his knowledge in effect.
Allah knows best.