Congrats!! I know you are very excited.

As for Tigger being and only cat for 6 years, Ripley was an only cat for 10 years before I introduced Jazz and then a year later Scout and now another year later R&R (the kittens Rocky and Rumor). He did best with kittens, Scout was almost a year old and they still fight, but he actually enjoys watching kittens play. Maybe you could talk your mom into two kittens so they'd keep each other company and not drive Tigger crazy. Even if you just get one he will adjust with time. Ripley did with just Jazz.