For the most part, animals are social beings. They want friends. They are happier with another animal in the home. There are always exceptions tho. Some animals have trauma and don’t want to be around other animals. And some of them just prefer solitude. Just like humans!
Things to keep in mind:
Relationships between the same animals will change over time and evolve like human relationships. Roles shift, aging and health change the dynamic, and changes in the home/lifestyle/etc affect the dynamic.
When there are relationship problems, most of the time, those can be worked out with a guardian’s help. (Again, exceptions are animals that have experienced trauma with other animals and will always need to be an only pet).

When there are relationship problems, the sooner a guardian steps into help, the sooner the problems will be resolved. Lots of things go on between animals that humans don’t pick up on, or don’t notice. They communicate with each other constantly.
They push each other’s limits so subtly at times it is hard for a human to see. They do disrespectful things so subtly, it is hard for a human to see. Sometimes they feel their space and their boundaries are not being respected by the other pet. This creates tension. Sometimes there is jealousy. Sometimes just a lack of patience because the other animals can’t take a hint. And other times, someone gets on a power trip. Relationships between pets aren’t always fair, just like humans. Animals do at times do things to annoy the other, or unintentionally upset or disrespect them.
Animals experience all the same emotions and problems in relationships that we do. But it is hard for humans to notice. It’s a different language to humans. That’s where animal communication comes in. Animals can tell me what the problem is and how to fix it. Then I can tell you and you can take the necessary steps to make sure the relationship gets back on track. Things of it as siblings upsetting each other, sometimes parents have to step in and help everyone feel better. It’s not taking sides. It just creating an environment where everyone feels their needs are being met.