It has been written [Rattray] that his mother, a Dwaben woman, was the obagyegyefoɔ of Asantehene Opemsuo Osei Tutu. Clearly, the logical inference from what we know is that Baafoɔ Amankwatia was probably born about the same time as the future King, which would have been how it was possible for his mother to assume the role of breast feeder to the future King.
From R.S. Rattray (1927):
Many Ashanti mothers do not feed their infants for the first two or three days after birth, but call in a wet nurse (obagyegyefoɔ), lit. 'one who receives the infant'. In the case of a child of the Oyoko or Royal clan, from which were drawn the Ashanti kings, this was always done. The woman so chosen was compelled to send away her own child and to nurse the royal baby. Such a foster-mother found great honour; she was fed on the best food and richly dressed; she might be given 'a stool' and subjects, and so become the founder of a new house. Her own child, which she had been compelled to leave with another woman to suckle, might also be made a chief. Many of the Coomassie [Kumasi] chiefs owe their position to this cause in the olden times. Afua Fofie [aka Afua Moku, a Dwaben woman], an ancestress of the present chief of Bantama, the Ashanti war lord, suckled the famous Ashanti king, Osae Tutu [Osei Tutu]. Afua Fofie was mother of Amankwatia who was created the Chief of Bantama.
Bantama stool is among the four stools in the Kumase state which enjoy paramount status. The rest are Akyempem, Akwamu, and Adonten stools. Bantama stool is the paramount stool for the Kontire division of Kumase state.
The first occupant of the stool, Baafoɔ Amankwatia I and his people were believed to have come from Sebedie, near Kokofu. Baafoɔ Amankwatia I, who was the first occupant of the stool, was a friend to Nana Osei Tutu during their youthful days. Oral tradition has it that when the king of Denkyira, Nana Boamponsem, needed a royal from Kumase to come and serve at his court, Osei Tutu was the royal chosen for that service. Osei Tutu in turn requested his friend Amankwaatia to accompany him to Denkyira. Amankwaatia willingly accepted the invitation and followed Osei Tutu to Denkyira where both of them served at Denkyirahene's court. Another version of the history states that Amankwaatia was a stool carrier of the Denkyirahene. It was he who saved Nana Osei Tutu when he impregnated Ako Abenaa Bansua, the sister of Denkyirahene. A secret meeting was held where it was decided that he should be killed for the action. However, Amankwaatia who was at the meeting divulged it to Osei Tutu and hurriedly ran away with him in the night to Akwamu. In either way, Amankwaatia was with Nana Osei Tutu both in Denkyira and Akwamu. They also studied the war tactics of the Akwamu people together.
[Ref: Osei Kwadwo, Part 2, Vol 1.]