A recent patch to Clash of Clans introduced the heroes: The Barbarian King and the Archer Queen. From the content SuperCell released I can see that they are immortal and can be used for attack and defense. The videos only ever showed one at a time though, other than when one was attacking and one was on defense. Is it possible to have both in the same village.
tl:dr Yes it is possible, but they have different town hall level requirements and costs, so you have to have a high level village with substantial resources to purchase both.
Barbarian King - Available at Town Hall level 7, and costs 10k Dark Elixir. This means you can potentially purchase him without spending money if you build and completely fill the Dark Elixir Storage which is also first available to you at TH level 7. Note that you can do this by spending gems, or by raiding - but you don't get a Dark Elixir "mine" till TH level 8. (It's painfully slow, so don't hold your breath waiting for it).
Archer Queen - Available at Town Hall level 9, and costs 40k Dark Elixir. This is substantially more than what your early Dark Elixir Storage can hold, so effectively you'll have a hard time getting her early on without spending gems. If you are very patient, or a very successful end game raider, then you may eventually get her without spending money.