Sister Sledge are nervous about the protocol if they get to meet Pope Francis.

The 'Lost In Music' hitmakers are ''honoured'' to have been chosen to serenade the Head of the Catholic Church at 'The World Meeting of Families 2015' held in Philadelphia on Saturday (26.09.15) but are worried about what they need to do if they have the opportunity to talk to him.

Speaking exclusively to BANG Showbiz, Joni Sledge said: ''We've been asking about protocol because I think just the fact that he is the Pope - someone who should be honoured - means there is protocol to follow. We definitely want to respect the tradition.''

The disco siblings - Joni, Debbie Sledge and Kim Sledge - were raised as Methodist Christians by their parents and first began singing at their local church, the Williams Temple Christian Methodist Episcopal.

Although Sister Sledge are not Catholics they have been following Pope Francis' speeches and sermons since his Papacy began in March 2013 and respect his humility and messages of mercy and agapeistic love.

Joni said: ''We're not Catholics but we believe in the Pope.

''We've been reading a lot of interesting things about him and he has a different approach to previous Popes. He's very open in terms of equality and that essentially we are all people. We are all in a position to do something great towards humanity. So we support him.''

At 'The World Meeting of Families 2015' event Sister Sledge will perform a special rendition of their classic hit 'We Are Family' as the song has become a mantra for peace around the world.

Other performers attending the event include Aretha Franklin, Jim Gaffigan, The Fray, Andrea Bocelli and Mark Wahlberg.