Sandor was quite a scary vampire that killed his own wife and children for blood. 

Trust me on this when I say he didn't mean to do it but he had voices in his head that urged him on. 

His wife was human who gave birth to twins that were half-lings. Surprisingly his wife survived the birthing process. They had one boy and one girl who both had their fathers hair and mothers eyes. 

As they grew they learned new things and started having cravings and that when Sandor started to hear voices.   

Every since the day he slaughtered his family he has hated himself and has been searching for a way to die so he can join his family and apologize.