When I was young, I found heaven difficult to picture. Adults said heaven was perfect, but what does that mean?
Do people wear white robes and float around with harps? Will angels sing praises to God from nearby clouds? Is it possible you are served double-decker, ice cream cones with sprinkles for breakfast, lunch, and dinner?
All good guesses, but more movie-like than heaven-like. The truth is heaven is so perfect it is impossible for our human minds to imagine.
Since you asked, I'm going to assume you have a pet you love greatly. I sense you want reassurance that you'll someday get to see your dog Fido, your cat Mousers, or (say it isn't so!) your creepy crawly tarantula which you use to terrify your mother.
I have to tell you, this is a question that bothers adults as well. When you are a Christian, it’s so hard to watch another Christian make bad choices. It often makes you question if they are truly a follower of Christ. Proverbs 13:5 says "The righteous hate what is false."
There are two sides to this question, though.