If the Senior package is priced higher because it involves X,Y and Z products or services that the family package does not, then the OP missed an opportunity to explain that, and sell it.
On the other hand, if his senior package involves the same products and services as his family package but with a higher price tag, then the OP got caught in his own pricing problem.
Hopefully the OP has learned from this experience and will take another look at his pricing, sales strategy and client communication. Otherwise this will happen again, with the same outcome.
I'll book a senior portrait session but if Grandma wants me to spend the 2 hours photographing her cat and run over the time allotted that's fine by me. We'll just book another session.
There's no such thing as a "two for" here. There's only a "whatever time allows" at my business.
+1 to both!
The only possible exception, is if its a ala carte type prints outside of the package. The reason for this is because there are certain things that obviously sell more than others, so if i spend 4 hrs photographing grandma and her kitty, i will not be making as much as if i spent 4 hrs photographing that newborn, were i not to price differently. Of course its my job to make my pricing clear and offer incentives related to each job so that it makes sense to clients.
So a package where alot of prints may be purchased, might have a lower entry price than one where few prints might be purchased. But this sort of stuff has to be clear in advance, if people don't understand your pricing, issues like this will come up constantly, and i don't think they're trying to pull a fast one, they're just trying to get their value's worth and you left them confused.