What is required to establish a joint tenancy with right of survivorship?

A "joint tenancy" is a type of concurrent estate that has a premium feature called "right of survivorship." Right of survivorship is the ability for living joint tenants to automatically absorb the interest of a tenant that dies immediately upon their death. In other words, if Amy and Bob are joint tenants with right of survivorship in Blackacre, it means they both have an equal interest in Blackacre. If Amy dies, her interest is immediately absorbed by Bob. Why is this important? Because it means that Amy's heirs do not inherit Amy's share of Blackacre.

Such a premium feature demands some pretty specific requirements in order to gain its ability. These requirements are called the 4 unities.

In order to establish that a joint tenancy exists, you must show that:

(1) The parties got their interest at the same time.
(2) The parties were given their interest by the same instrument (meaning, they were deeded the interest in the same deed)
(3) The parties have the same interest in the property, meaning they have the same type of interest and the same duration of ownership, and
(4) The parties have the same rights to possess the land.

If these 4 unities are present in the fact pattern, and there is a clear intent that the parties get the right of survivorship, then it is established and waits to kick-in upon the death of a tenant.