companionate

Designating a proposed type of marriage (or other partnership) in which the partners plan to have no children and take on no legal obligations to one another.

Friendly, companionable.

Pertaining to a (chiefly romantic) relationship that emphasises companionship and mutual respect.

Gradually it evolved from an economic enterprise to a companionate one—a free-choice engagement between two individuals, based not on duty and obligation but on love and affection.