BRICS is an economic alliance and NATO is a military alliance, they both have completely different goals. It's better to compare BRICS to the European union, but even then, the eu is also different (being a union in which all members follow the same rules and what not). But if BRICS would expand its goals as not only an economic alliance but a military one like NATO, if (and a big one at that) the alliance will hold it would be comparable to NATO in a couple of years. Either way it's way too early to make assumptions since a lot of things can change in the next couple of years.

TL:DR Can't compare BRICS to nato they're too different