This site claimed that the phrasal possessive in English came from French influence, while the synthetic possessive is Germanic.
Germanic Pattern: the king’s son - cf. German "des Königs Sohn".
French Pattern: the son of the king - cf. French "le fils du roi".
It would make sense since the latter is common in Latin grammar, while German uses genitives and also the -(e)s. However, in Scandinavian languages, whose ancestor had lasting and important influence in English, I have seen in some cases a similar pattern to the French one, but since I don't speak those languages I can't be sure. On the other hand, it would not be the only grammar change that French put or accelerated in English.
What is the origin of phrasal possessive in English?