At first I agreed with everyone else...Jake was your first dog and should get priority in your home. We have said as we added Cincy and Spot, if there was a problem with Sadie, she was here first. Thankfully we have not had to face that, she loves her brother and sisters immensely.

Hearing more about where Jake would be going (with family), it may be the right choice. If you are truely doing this for him, becuase he would be happier, than maybe it is the right answer. I don't agree with with rehooming Jake in order to bring a new dog in, however if he would be happier AND you can bring another dog in, I can understand that.

Only you know the whole situation and you have to do what you know is best for all the dogs involved.