United have signed identical twins as future full-backs.
Fabio and Rafael Silva have both signed pre-contract agreements from Brazilian side Fluminese.
The youth internationals will join up with United on July 9, when they turn 18.
Rafael revealed it was Cristiano Ronaldo who sealed the deal.
Rafael Silva (right-back) said: "When we were negotiating, Cristiano Ronaldo phoned us saying that Manchester United was a tremendous club and it was a wonderful place to play football."
Left-back Fabio said: "We were there to be familiar with the club and we played part of a friendly match.
"We were on the same pitch as Rooney and Ronaldo. They were very kind with us."