I have 2 Shelties who are 12-year-old half-siblings. Although they show love, trust & respect for us both almost equally, they both have a mild preference, as the male acts like a mama's boy & the female, I'm writing about, acts like a daddy's girl.
She starts watching the door & howling non-stop usually about an hour before it's time for him to come home but now & then, her clock's off & it starts even earlier. She sounds like she's heartbroken & it's heartbreaking to hear & a bit aggravating as well! I've tried consoling her, as well as trying to distract her in various ways but she just remains singularly focused on his return home, no matter what I do!
When he has to take business trips for the weekend or longer, her moping & howling becomes an utter nightmare! Once he's home, everything is set right again in her little doggie world & she's fine but my nerves will be beyond frazzled. The male pays no attention to her Eeyore-like behavior & he'll happily greet my husband but nothing out of the ordinary.
As for mild preferences, I mean if thunderstorms or anything makes them anxious, he wants to be glued to me & she's glued to my husband, they both prefer my husband for playing & both prefer me for petting, scratching, etc. They both prefer him for walks but both only trust me to go in the pool with them, etc. so no real major differences there.
She has no current health problems although she contracted encephalitis/meningitis twice in the past & fully recovered both times & with no other behavioral issues. I've tried being as thorough as possible because I'm really hoping someone can help me & her!