Pepper was meowing and scratching at the door for almost half of the night. Furthermore, he attempted to open it by pawing at the doorknob. I'm not sure if it was out of curiosity, or it he was scratching as a sign of "marking his territory." My husband and I decided to give it a shot, and let them have their first face to face interaction. I held Pepper in my arms and took him into the room, and allowed him and Blackjack to look at each other for a bit. So far, there was no hissing, growling, just staring at one another out of curiosity.
Then, later this afternoon, I decided to spend some time with Blackjack in the room. He was being affectionate, by rubbing on me and walking on my lap a bit. He didn't try to paw me this time, so I started feeling a bit more positive. Then I opened the door to leave the room, and he began hissing at Pepper again. (No hissing from Pepper today though. In fact, he ran away from the door, and behind the sofa.) I distinctly remember my friend telling me Blackjack gets jealous when she holds kids, so it could be a case of jealousy that I'm giving Pepper attention. I started getting hopeful this morning that both kitties are slowly getting used to
one another, but I guess it could go either way at this point