the magical heritage

Morganna cursed her family line to be squibs until someone is seen as worthy of her family magic, this is because she had a daughter morgan le fay, which she did horrible things, and do to the similarities to her mother, no one knew the difference, and no one knew morgana had a daughter in the first place, and merlin, the greatest sorcerer had killed morganna wrongfully, but she casted a curse on her line, for them to all be magicaless until one person down the line is seen as worthy of her magic, which when the time comes, all the people in the family line that were seen as unworthy, their magic wast destroy, it empowered the curse, and once it found someone worthy, all that magic would embed itself into the redeemed Le fay.