Nobody knows for certain what could cause the big bang. However, there are two theories that scientists developed in the late 20th to beginning of the 21st century. They are String Theory and M theory. The M stands for Membrane.
String Theory posits that what we call particles/antiparticles are just vibrating strings in extra dimensions other than the familiar space-time. M-theory posits that our universe is sitting in a 3-D membrane (one of many parallel membranes) embedded in a higher dimentional space. Particles are still strings but have endpoints that must be on the membrane. Adjacent membranes are are a microscopic distance apart and all membranes constantly warp ever so slightly. If two membranes collide, a Big Bang occurs giving birth to two universes, one in each membrane.
Just imagine if the two formed universes differ by only there being an antiparticle in one universe for each corresponding particle in the other and vice versa, but with no difference with the relative motion/interaction of the contents. Then it would mean we have a twin universe where there is an anti-earth with an anti-you and an anti-me on it living the same lives as we do here.