This question is about our recently adopted former foster dog, Calvin (Nitro). Although he has been in the house for almost 4 months, and has made great progress with his resource guarding. For example, he no longer snarls and tries to attack another dog who nonchalantly walked past his crate while he was chewing on a Nylabone. Calvin now pretends like they don't exist when he's locked in his crate which he always is in the case of chewies, food or water. Toys are rigorously controlled and are used only for interactive play with humans. He also is now housebroken and gets along with or at least tolerates the other dogs in the house with supervision only to make sure of no fights or bullying.
Which brings me to my question, this 5yr lab will only play with me outside of the house and throws a fit if anyone other than me tries to take him out of the house (even to go potty). He put his front paws on the sides of the doorframe and sat down when my 9yro daughter tried to potty him, whining and screaming until I ordered him to go will her. He also starts whining the minute I get up in the morning but settles down when I tell him to "Quiet", and for a few minutes after I get home from work. He is crated while I'm gone because he's calm then instead of trying to constantly look for me. In the house, Calvin is friendly and outgoing with all members of the family but outside he only has eyes for me. Should I be concerned or is Calvin going to be like Hobbes and be considered my dog only?

Do you both sometimes go, gradually giving the leash more and more to the other family member but you still there for now, and reducing your involvement gradually?

For now with my daughter, yes, as it's frustrating for her when she's in helpful mode to try to deal with a dog that weighs as much as she does but doesn't seem to understand that he should go with her. I've also put her in charge of his favorite game toy on a string in order to try to get him to bond with her at least. We tied a long string onto an old teddy bear on one end and tied the other end to a wooden dowel to make it. Calvin has to sit or down to get her to twirl it but it's guaranteed chase, grab and shake a couple of times. I hang around to make sure he outs the toy when told too and that he doesn't get to wild. He walks fine on a leash with her holding it as long as I walk on one side of him but if they get ahead of me, he sits, spreads his feet far apart, whines and refuses to take another step until I catch up.
With my husband, no as it doesn't seem to bother him too much and he seems to think Calvin just needs more time to settle in.

Intially, when he first came to live with us, I was his primary handler as his behavior around food and water gave us reason to be concerned. He would snarl at our dogs if they walked by the baby gated room where he was locked in his crate while eating or drinking. Thankfully that behavior has disappeared. Although he had never shown aggression toward humans, I wanted to be sure he was okay and had least know an "ouT" command before I let my daughter do anything with him. Maybe I was too cautious, as he is still too hectic around food so kibble is used when I have too use introduce a new behavior but I switch to a toy ASAP and my daughter only uses the ball or other toy with him.