Wales coach Warren Gatland has recruited his son - Highlanders first-five Bryn Gatland - to help them prepare for their crunch World Cup semi-final with South Africa.
Wales asked All Blacks head coach Steve Hansen for special dispensation for Bryn to train with them, as he is eligible for the All Blacks, UK media are reporting.
He is not eligible to play for Wales.
The 24-year-old trained fully with the Welsh team, reportedly his first full session since badly breaking his foot while playing for the Highlanders against the Sunwolves in Tokyo in April.
In a coincidence, Bryn sustained the injury at the same ground where he trained with Wales - the Prince Chichibu Memorial Stadium.
Warren Gatland is tipped to guide the Barbarians against Wales late this year. Despite the injury, Bryn is in line to play for that team, giving his father the opportunity to coach him in a top side for the first time.