Very nice, but that actions have restriction age?? I mean, if we do the scheme, the objective family will let us marry with men/women of 18-40 `fertile years´ or we will marry with elder people incapable to procreate??There are a few different outcomes. Nothing is set in stone in this world, they could even refuse (though their head of family would have to be quite disloyal for this)
Generally marrying your ruler or heir into another family will make them quite happy and will help with their loyalty, but could well make other families upset since they were passed over. You have control over which family you ask when you start the scheme.
Refusing the match they find for you will also not endear them to you.