I am flying from Paris to Mumbai, with a transit at Brussels, with Brussels Airlines throughout. I have 60 minutes to get on the next flight at Brussels.
Is this sufficient?
From Brussels Airlines:
Connecting at Brussels Airport is easy since there is only one main Terminal.
If you are already in possession of your boarding pass for your connecting flight, you may proceed directly to the gate. When exiting the plane, do not forget to check the flight information screens for your departure gate. If you need to get a boarding pass for your connecting flight, please proceed to the nearest Brussels Airlines Service Centre.
An hour sounds ample and, by the sound of it, the airline's problem rather than yours if anything were to go seriously wrong. I'm assuming you are on a single ticket (Paris>Mumbai) so your luggage will be checked through and you will probably receive your Brussels>Mumbai boarding card in Paris.
Even for entering Schengen from outside qaminari at Trip Advisor acknowledged (02 May 2015, 10:22) 30 minutes could be enough:
the minimum "legal connection time" at BRU is 50 minutes and changing from non-Schengen (UK) to Schengen (France), which means from Pier B to Pier A, with passport control in between, I personally would prefer to allow 1h30 - even if, on a good day with the wind behind you and no delays or lines (and running down all the walkways available), it is possible to do this in 30 minutes.
(There are only two piers at BRU.)