When people think about property they own with another person (or persons) there are two distinct ways that that piece of property can be owned. The first is as joint tenants, which means while they own the property equally, there is a right of survivorship attached so that on the death of one of the owners, the entire property automatically transfers to the other owner by operation of law. Ultimately, this means that property which you own as a joint tenant will not be covered by your will if there are other owners still alive. The property will automatically go to the other owner and may be covered by his or her will. Naturally, this may not be your desired result.
The second way to hold property is as tenants-in-common which means each owner has the right to a specific percentage of the property (most common is 50-50). When property is held this way, an owner can transfer his or her interest to his own heirs- it will not automatically go to the other owner.
Knowing the difference is key, as most institutions, such as land titles, will assume the property is held as joint tenants unless otherwise indicated. This is likely due to the fact that the vast majority of shared ownership property is between spouses who would prefer the survivorship aspect of joint tenancy to avoid potential taxes on disposition or probate fees in those provinces that charge probate fees based on a percentage of the estate (Note: Alberta does not do this). However, your estate and therefore your wishes can vastly change depending on the ownership type. Make sure you know how your assets are owned when you create your will!