I was looking for a manga I was reading about 5 years ago. The MC was a member of a family of cultivators including 2 brothers. The MC had blue hair just like his older brothers. I remember one of the brothers was supposed to be leading an army at one point and the MC arrived to save his brother. Not much to go on I know but the family was also supposed to be looked down upon for some "sin" the MC or MC's family did during the series. Edit: after sleeping I remember something about a medusa joining him. Or at least that is what they called her and she kept referring to herself as a "Queen".

Xingchen Bian?

~4400 manga completed
~1700 ongoing...

Then it most likely is Doupo Cangqiong...

~4400 manga completed
~1700 ongoing...

Yep! That's it.