Three Brothers Spoil Me Episode 7 shows that the Lancaster brothers indeed mistook Mia, who wore the necklace, for their long-lost sister. Their sister disappeared 20 years ago, and the necklace was the only proof of her identity. Mia realized Nancy was likely the true Lancaster heiress, but Mia planned to steal her identity. When Nancy returned to reclaim her necklace, she asked Mia to return it.
