Thank you all for your answers. We've been following your advice, and I can tell things are slowly improving day by day.
We did a lot of room-switch, let them play with a net in between, and allowed supervised time together. We finally have also permanently let the little one's door open.
Hi everyone, and thanks in advance for reading.
Doro and Tiana (male and female) are the two kittens living at home, they both are three and a half months old.
He was picked up from the street when he was around 7 weeks, he is growing healthy and full of energy.
We thought that feline company...