I went to perform Hajj this year and I was unable to do the last portion which was the farewell due to the menses and my brother has said that it does not really matter if you did it or not. I want to know that my Hajj is complete or not and do I have to do it again?

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.

The woman who is in her menstruation period does not have to perform the farewell Tawaaf.  The evidence for this is the Hadith reported by Ibn Abbas (Radiya Allahu Anhu) that the Prophet (Sallallahu Alaihi wa Sallam) "Ordered people to make the Haram Mosque be their last place before leaving Makkah.  But he eased that matter for the woman in menstruation period". [Al Bukhari and Muslim]

Al Nawawi said while explaining this Hadith: 'This is clear evidence that Farewell Tawaaf is an obligation except on the menstruating woman.  The latter is not asked to perform it and does not have to expiate for that.  This is the opinion of all four Imams Malik, Al Shafi’e, Abu Hanifa and Ahmad as well as all the other scholars'.  So your Hajj is valid, Insha Allah. 

Allah knows best.