Is my kitten too lonely at home?

I work long shifts as does my housemate, so there can be times when no one is home for 12-15 hrs in a day. We ended up getting two kittens about 7 years ago so they could keep each other company. I don't think cats get very lonely in 12 hours or so, not like dogs. I think having two cats relieves boredom as they play, fight and wrestle with each other, thus getting stimulation. However, after longer stretches of absence like a day or so my cats do appear to have really missed me.

Yes. Your kitten can definitely get lonely when you're gone. A kitten's sleep is broken up by many short bouts of play. Your kitty is used to playing with you, and now you're not there. I work at an animal shelter, where I always tell people who are adopting a kitten that they need to adopt two. Most who decide against our suggestion are back within a month to get another kitten.

If your current living situation is not allowing you to have another cat, then you are doing the right thing by leaving toys and giving the kitten plenty of things to do while you're gone.

Be sure you have a tall cat tree (6-7' tall), with different levels the kitty can climb on. Even though he's a kitten, he will very quickly grow into a tall cat tree, which will give him climbing exercise to wear him out.

I would also suggest that you give the kitten a new toy or a favorite toy each time you leave. When you get home put the toy away. This associates something good and exciting with you leaving.