amulet of the blooded says the following:
"If a creature that already has the associated bloodline wears the amulet, the wearer does not gain the abilities listed below; instead, the effective level of his bloodline powers increases by 2. This effect does not stack with other abilities that increase the effective level of bloodline powers."
Does other abilities count Robe of Arcane Heritage which states:
These elegant, dark purple robes are usually decorated with gold stitching suggesting a particular sorcerer bloodline, though some might indicate a family tree. When a sorcerer dons a robe of arcane heritage, the stitching pulls itself apart and reweaves to match her particular sorcerer bloodline. The wearer treats her sorcerer level as 4 higher than normal for the purpose of determining what bloodline powers she can use and their effects.
Would they stack?