One can 'force' a dependant to make an eruv t'chumin. Since they are only made for a dvar mitsva this is considered like forcing him to do a mitsva which one who has the power, has to do. Normally ...
The Mishna (Kiddushin 1:1) tell us that one can acquire a wife through money (kinyan), documents (shtar) or biya (intercourse). The first two are commonly used to buy and sell regular objects, but ...