All dogs are different as far as personalities and the way they react to things. We had Jake for a year when we decided to get another. Jake is very much a mama's boy, and we spend alot of time together playing. I was a little worried about how he would react to having a new pup in the house, but I made sure that I paid the same amount of attention to both. Jake did get a little mad at me, and he wouldn't sleep next to me or sit with me for a few days. But, I just kept paying lots of attention to him, giving him lots of affection and praise. Within a few days, he was back to himself and was having lots of fun playing with his new brother, Jackson.
The two of them play together A LOT, but Jake still likes to play with me the same as always. They do get a little jealous of each other. I try not to make a big deal out of it, and I give them both the same amount of affection. Jake actually seems much less jealous than Jackson now lol.
Getting a second yorkie didn't change Jake's personality. He is still the same. It takes time for the two to get to know each other, etc. Some take longer than others. I was really happy with the way things worked out for us, and I would even love to have a third!