"It's Valere's choice. He made the decision a while ago to join OM," Germain Snr, a defender with Marseille during the club's golden era in the 1990s, told La Provence newspaper.
Marseille have yet to confirm the recruitment of the 27-year-old forward, who scored ten goals last season to help Monaco lift the Ligue 1 title.
Germain was however overshadowed at Monaco last season by teenage sensation Kylian Mbappe.
French media are reporting the transfer to be worth in the region of 10 million euros ($11 million).
"The club has been close to his heart since he was a child. He always said he wanted to join Marseille," added Bruno Germain, who won the French league title three times between 1989 and 1991 and finished runner-up in the Champions League final in 1991.