When Bert called Dave, he had just escaped from the young lady, who was currently having breakfast with Tiffany.
That's why he told Dave that they had a pleasant time together, and why the young lady affectionately called him "Uncle" when she answered the phone and casually mentioned she was there as a guest.
The young lady's calling him "Uncle" made Dave frown on his end. His first instinct was to correct her address for Bert, but then he realized it was probably her mother who had told her to call him that, or else she wouldn't have known the term.
Upon further thought, he realized that his daughter calling him "Uncle" wasn't entirely wrong...
After all, Bert was indeed his older brother by blood, a relationship that couldn't be erased.
So, he suppressed his emotions and said to his daughter, "Mom and I are busy with work right now, but once we're done, we'll come to pick you and Lady Tiffany up to go home."