My girlfriend recently got 2 cats (sisters from the same litter) from an animal shelter.
They are 3 years old.
At end of May we went on vacation, and on our return we discovered to our dismay that they started peeing on her bed regularly (there were several stains).
Since then, the bedroom is not accessible to them.
A couple of weeks ago we bought a tunnel with a resting "pillow" attached to it. 3 days later we found pee on the pillow.
In the intervening time period, despite being a sofa with a surface that would absorb the pee available to them, they never pee-ed outside of the litter boxes (they have 3, we clear them twice a day).
Also, they passed their yearly visit with the vet just before she got them.
The diet has not changed, we are giving them the same food the shelter was providing, as suggested by the volunteers at the shelter.
As my girlfriend and I are thinking about moving in together, we are worrying that the cats will pee on even more furniture that has a similar texture to the pillow and the cover that was on the bed.
Are there methods to dissuade them from peeing outside the litter boxes?