Hi Mouserocks,
I had asked that same question here some time back when I was working on my story "Full Partners." The bottom line of that thread was that the age difference had not been specified on the show, so you can do what you wish with it. All we know is that Lois is sufficiently older than Lucy that she was able to take care of her sister when neither of their parents were doing so.
Joy,
Lynn
edit: If you are interested, this is
the thread I was referring to.
