Hi and welcome to YT

. I'm sorry it's under these sad circumstances, but I hope you find some support and understanding and compassion here.
I must say that to me, you sound just incredibly wonderful and I think you're awesome! To love this little man
this much, and truly consider him your grandpuppy (as my in-laws consider ours too

, which I love!)...well, it just *breaks* my heart that he is not with you. If it were up to my magic wand, he would be with you full time. You and Prince sound like you belong to each other, ya know?
I can only hope that if you really have a gentle, honest, forthright conversation w/ your daughter, that she will then understand your love for Prince and would be willing to let you have some meaningful time with him. If I was her, and you told me your heart was kind of breaking/aching bc you couldn't spend time with him anymore...well, I would then sure be open to sharing more of him with you.
What about exploring ideas with her like...you taking him for some weekends? Or splitting half-weeks with her? Or taking him every other week?
My gut says that the couple don't *truly* want this little man in the same way that YOU do....I feel this bc his coat is somewhat neglected and bc he seems "lethargic" and un-engaged/sad.
I SO hope she will open her heart, be honest, and allow you to love this little man to your heart's content. What a GREAT Christmas present that would be, eh? In fact, maybe you should tell her that's all you want for Xmas, is time w/ your beloved grandpuppy.