If the deeds show that they're 'joint tenants' they both own the whole house. If one of them dies nothing is 'inherited' or 'transferred'. The surviving aunt automatically owns the whole house.
If the deeds show that they're 'tenants in common' they both own a share of the house. (Unless the deeds specify otherwise they'll each own half of the property). Each aunt can leave their share of the house to whomever they choose, in their will. If an aunt dies without leaving a will, the rules of intestacy will apply.
Chris