Where two or more parties to an agreement declare or agree to be jointly and severally liable, they are agreeing that each person accepts liability for the whole debt not just for a proportion of it.

Property owned by more than one person is owned either as joint tenants or tenants in common.
If the owners opt for a joint tenancy, then they each own the whole of the beneficial interest, which means that the survivor of them will have an automatic right to the property on the death of one or others of them.
Under a tenancy in common, each tenant in common owns a specified share of the beneficial interest. On the death of a tenant in common, their specified share will be dealt with in accordance with the terms of their will, or under the rules which apply on intestacy.