Responses
That's how people normally do it when they have more than one dad lol Dad, Daddy, Father, Papa, Papi, Pops, Old Man, or even special nicknames would be better.
I've seen someone call their dad Nags before and I thought it was hilarious, but they really cared for each other LOL
I really don't like the first and second system either.

I don’t like how Titi calls the other dads “second/third dad”. It would be more special for each dad to have their own endearment like daddy, father, papa. It seems like there’s a ranking on my opinion.