Hussain is the diminutive form of Hasan. Hasan means good and beautiful. It is good name. You may keep it as this name is not the sign of Shias. The scholars of Ahl Sunnah al-Jamah have been keeping this name earlier and later, therefore what some relatives say is not alright. You should pay no attention towards them.
Allah knows Best!
Darul Uloom Deoband