Brittney Griner's brother and sisters have encouraged ... they already had a full house with three kids. Her older siblings ...

Brittney Griner became the first player in Unrivaled history to dunk in a game Monday night then shared the moment with WNBA legend Lisa Leslie.

Brittney Griner was Baylor University's star basketball ... The coaches thought if it seemed like they condoned it, people wouldn't let their kids play for Baylor," Griner stated.