In our case it was the other way around, we had our little Piper 1st and then brought in my sons toy poodle. Piper was not very accepting at first and over all it took 5 weeks for them to become compatiable but it did happen, walking them together and playing and showing them equal amounts of love and play time I think helped alot. Also showing Piper that it was time to share spots on the bed etc helped her to realize whe was not loosing her own spots just letting someone else enjoy as well, after a year of having them together Piper now waits by his kennel in the morning for us to let him out so they can go outside together. So yes things can turn around and your older one will probably end up being protective over your little yorkie