Most contracts involve one person promising one thing and another person promising another thing. For example, in a tennancy agreement the landlord's obligations to the tenant are different from the tenant's obligations to the landlord.
Historically, marriage has been viewed in a similar way. The obligations of the husband to the wife are not the same as the obligations of the wife to the husband. The vows made by the husband differ from those made by the wife. In the traditional English marriage service (Book of Common Prayer) the groom's promise is to love, comfort, honour and keep the bride, whereas she promises to obey, serve, love, honour and keep him. There is also an explanation of the differing duties.
More recently marriage has been thought of as a relationship in which the duties of husband to wife are identical to the duties of wife to husband. In the modern alternative Church of England marriage service each promises to love, comfort, honour and protect the other. There is no difference.
Is there a legal term or phrase for a contract where the commitments of each party are identical, as opposed to being different.
I am not looking for a word like "equal" implying the status of the parties, or "symmetrical" implying, I gather, their relative bargaining strength. I hope for a word or term that means the commitments are identical.