Do you automatically call new additions to the family by their title because it is official, or do you only do it when it feels natural?

I love that the holidays bring out family fun drama.

I just got into a disagreement over the phone with my dad, who thinks that it is disrespectful that I don’t refer to my aunt’s new husband as “Uncle SoAndSo.”
The thing is, I’ve known this man for many years as my aunt’s boyfriend, and only called him by his first name. I am thrilled that they got married, I’m happy for them, I like and and I care for him… but calling him “uncle” just feels really weird.

Is that really disrespectful? Am I wrong about continuing to address him as I always have? I am really close with my aunt… should I ask her if he feels put out because my siblings and I don’t call him “uncle?”