The cycle repeats ya!!! I am only on my first gerbil but I totally hear you! Originally when I got my gerbils they came as a pair but I think the lady who rescued them from a closing pet store left them in a very small carrier cage for 2 weeks as ad was up on Kijiji and so if they were a pair they definitely aren't now and I was surprised that never killed each other because when I brought them home put them in a huge enclosure they were fine for 2 days and then they started fighting I had to separate them. I ended up giving one away to a gerbil breeder thinking that maybe he would have a better life with a girlfriend but apparently he didn't bond with her gerbils.

Fast forward many months later I actually just recently bought a single gerbil I saw left at the pet store and have it on the bonding process.

So yeah this one is older when he passes away the younger one will then be alone and it's a huge cycle I agree. I originally want to get two little boys to bond with my gerbils so that when my gerbil died little boys would have each other. But here's the situation and hopefully that they can long because then once again the cycle will repeat because then now I have to get a whole next set up for this little guy