Well, two events can actually take place within this one event. So two outcomes, we either get a tails or we get a head. And in a way we can see those two outcomes as two mutually exclusive events because once this actually takes place and I get tails, then heads cannot actually take place because tails already took place. And that's what we mean by two mutually exclusive events. So flipping a coin once we obtain heads and obtaining heads is mutually exclusive to obtaining tails because either one takes place or the other takes place, both of those events in that single coin flip cannot actually take place. And in the same analogous way, having one child also creates two mutually exclusive events.