I would like to chime in and say that Doodlebug bothers Truman (my foster pup who is very old) but only when they are outside in the yard. Maybe instead of bringing home a rehomed puppy you could consider an older pup who is out of that playful crazy stage and is a little more calm. Pebbles and Bogey who are both 2 plus pretty much leave Truman alone

unlike the bratty Dbugs. It might be a nice compromise. Then when it comes time that your Kati is no longer with you, add a puppy with the young adult. Just a thought.......