All the stars in a multiple were born at the same time, and probably started off with the same chemical composition. But they also probably were born with different masses, so they did not evolve the same way or at the same rate. (The more massive a star is, the faster it evolves.) A sunlike star in a binary system with a much more massive partner might have its retinue of planets vaporized as the heavier star went through its giant stage, or even went nova. In a close binary, any planets of either star would probably never have a chance to develop life, unless they were both low-mass stars.

However, not all binaries are close binaries. In the Alpha Centauri system, the planets around A and B probably had too variable a history to have nurtured life. However, at Proxima (providing its orbit is roughly circular and doesn't come too near its primaries) a life bearing planet might evolve.

What we don't have to worry about is "pinball systems". Multiple stars form out of their birth nebulae in a morphological hierarchy. Two stars orbit a common center of gravity. Add a third star and it orbits far enough away that it sees the other two as one gravitational attractor. Add another and you get either two stars orbiting the central pair (like two satellites orbiting a planet) or two pairs orbiting each other (One binary star in orbit around another binary star).

Although higher numbers are physically possible, like three stars orbiting equidistantly from each other, they are higly unstable and easily perturbed. The stellar multiples are always pairs, two centers of gravity orbiting each other, (although each center of gravity may consist of multiple CGs as well.

This is the famous double-double, epsilon lyrae, two double stars orbiting each other. You will note that the separation between pairs is much greater than the separation of each pair. This is what I mean by "hierarchical".

I believe the most complex multiple system known contains 11 members, but others may have been found even greater by now.

The separations can vary enormously, in some cases, the pair is in actual contact, and exchanging material at the Lagrangian point between them. (Contact binaries)

In cases like this, the two stars actually affect each other's evolution, and the system itself evolves. For example a star can enter its red giant phase and swell up to fill its Roche lobe, at which point it starts transfering matter to its partner. Remember, the size of a star is not related directly to its mass. The smaller star may be much more massive. And stars will change size as well as temperature(color) as they evolve. And many stars vary in size and brightness over very short time periods, between hours and months, oscillating due to complex internal instabilities.

There are many strange creatures in this zoo.