I agree with zmjezhd. If you want to say "...he thinks both life and I are interesting", the least awkward would be "He thinks life is interesting, and that I am, too." It's not a phrase you're likely to encounter very often, though.

I would concur with zmjezhd, also, about the pen sentence. Whenever possible, write as simply as you can. "I bought a blue pen." Think of it this way: "Me compré un bolígrafo azul." or "Me compré un bolígrafo que es del color azul." Which sounds more natural? :0)