Beyoncé Celebrates Rumi, Sir Carter’s Birthday at Cowboy Carter Tour

Beyonce's poignant message to rarely-seen son Sir and daughter Rumi onstage in London

Beyoncé's daughter Rumi, seven, sobs as she joins her superstar mother for emotional moment on stage during her Cowboy Carter Tour in London

Beyoncé makes a surprise move after failing to sell out seats on the UK leg of her Cowboy Carter tour