As far as heaven goes, what we hear of it is our earthly concerns are gone, IE there is no marriage in heaven except to Jesus. If there is a similarity there that compares to here it's going to be about the business of God, about Jesus and ultimate peace within that. I suspect ( as someone said already, nobody really knows) all the pets you enjoyed on earth will be of no concern there. Anyway I love all the cats we ever owned but cleaning litter boxes is not on my bucket list of hopes and dreams for heaven.
I suspect just like for the Christian on earth it's going to be more about Jesus and the things of God than us there. But it says in scripture that we will be like Him and joint heirs to the throne.It says we will know what He knows and right here right now in my present body and situation in life on earth I find that a bit overwhelming to think about.
I think people are going to find heaven vastly different but in good ways from what we imagine here in this life. Old pets included ? I have no idea, I just hope they don't poop a lot if so. I think our earthly concerns and interests will be changed. I was wondering if there might be like a 100ft grand piano to play there or something like that. If there is, I'm sure it's played to the Lord.
We know there are different positions in heaven and different tasks according to our rewards on judgement day. We all make it to heaven who are born again but we don't all have it the same way or in the same place. We know there are three heavens or we could say degrees of heaven. John was taken to the third heaven, this indicates at least two other prospects besides before the throne room of God. It also indicates they are separate from hell. A bigger question than pets might be where in heaven will I be and what will I do there ? Well that's based on what rewards you have stored up in heaven, how you operated within your Christian walk, where your heart was at in Christ here on earth. These things are written in scripture.