Fëanor claimed the Silmarils for himself only very loud and clear, but come think about it, was it true at all that the credit for creating them belonged to him solely? It was Yavanna and Nienna who at first brought Telperion and Laurelin into existence, the very same trees which provided Fëanor the materials to make them from, the pools of light. And after he had created them they were brought to Varda to be blessed so no hands with evil intent could touch them without burning - a powerful enchantment which wouldn't spare even Morgoth's hands. So that would make four people which affected the birth of Silmarillion. The Silmarils eventually burned the hands of Maedhros and Maglor, and that's how they knew that the oath Fëanor made them take had become void. Varda wouldn't have the say though such power only because she was a Valie, but also because she had a part in their making. In other words, as one of the makers she had the authority to annul the oath and Fëanor's words alone weren't enough to make the oath last.