Believe it or not the way you own your property is very important if you want to leave a share of it to somebody in your Will.
Owning as "Joint Tenants"
This way, neither of you owns an identifiable share of the property. You collectively own the whole thing - essentially you hold it on trust for yourselves. This means that when one of you dies, the property automatically passes to the survivor(s). It does not matter whether or not the deceased co-owner had a Will.
Owning as "Tenants in Common"
By owning this way, you each own an identifiable share of the property. Unless you have stated otherwise, this will be 50% each for 2 owners or one third each for 3 owners etc. You are each free to use your share in any way you want. You can give it away during your lifetime, or can leave it to someone under your Will. Owning as Tenants in Common, the property will not automatically pass to the surviving owner(s) so it is vital that you each have a Will.