Flatmate helped with rent and bond, but now claims part ownership of one of my Shiba Inu puppies — what should I do?

Hey everyone, I’m looking for some advice about a weird ownership issue with my two 5-month-old Shiba Inu puppies.

When I first got them, the total cost was $5,000. I personally paid $2,500 for one, and my flatmate sent me $2,000 for bond and $500 for rent (not for the dogs). There was no written agreement saying the money was for ownership — it was just a living arrangement setup.

But now he’s saying he should “officially own” one of the dogs because he helped pay money around the same time I got them. Both dogs are microchipped, registered, and fully paid for under my name — I’ve covered all vet visits, food, and training since day one.

My concern is that he hasn’t been a responsible caregiver at all:

He’s given them alcohol mixed with Coke,

Feeds them human food and random snacks outside their feeding schedule,

Disrupts their training when he’s around.

He works FIFO and is gone most of the time, so I do 100% of the care. I’m happy to pay him back the $2,000 if it keeps things simple, but I don’t want him listed as an owner or having any control over the dogs’ wellbeing.

My questions:

Has anyone dealt with something similar — where a roommate claims ownership just because of money being exchanged around the time of adoption?

How can I keep things civil while protecting my dogs’ safety and stability?

Should I just repay him and make it clear legally that they’re mine?

I’m not trying to start drama, I just want what’s best for the dogs.