Which and why?
[name_m]Peregrine[/name_m] [name_m]Jack[/name_m]
[name_m]Thaddeus[/name_m] [name_m]Jack[/name_m]
[name_m]Theodoric[/name_m] [name_m]Jack[/name_m]
[name_u]Roscoe[/name_u] [name_m]Jack[/name_m]
[name_m]Bernard[/name_m] [name_m]Jack[/name_m]
[name_m]Rafferty[/name_m] [name_m]Jack[/name_m]
or
your suggestion
[name_m]Peregrine[/name_m] [name_m]Jack[/name_m] is nice! It’s got a smooth feel and lots of nickname options, it’s very cool. I like the idea of [name_m]Theodoric[/name_m] [name_m]Jack[/name_m] but maybe a different Theod- name might flow better, like Theoden [name_m]Jack[/name_m]?
I like [name_u]Roscoe[/name_u] [name_m]Jack[/name_m] and [name_m]Rafferty[/name_m] [name_m]Jack[/name_m] the best
[name_m]Peregrine[/name_m] [name_m]Jack[/name_m] is cool too
Not a fan of [name_m]Theodoric[/name_m]
[name_u]Love[/name_u] [name_m]Peregrine[/name_m] [name_m]Jack[/name_m]! So handsome and sweet.
I also like [name_m]Rafferty[/name_m] [name_m]Jack[/name_m] and [name_m]Thaddeus[/name_m] [name_m]Jack[/name_m]. I want to like [name_m]Theodoric[/name_m] [name_m]Jack[/name_m], but theres just something off. I like the suggestion of Theoden [name_m]Jack[/name_m]!
I really like [name_m]Caspian[/name_m] - but people here will probably think of [name_m]Caspian[/name_m] [name_u]Lake[/name_u] and [name_m]Caspian[/name_m]/pijan has rather unfortunate rhyme.
I love [name_m]Rafferty[/name_m] [name_m]Jack[/name_m] and [name_m]Thaddeus[/name_m] [name_m]Jack[/name_m]!
Suggesting [name_m]Phineas[/name_m] [name_m]Jack[/name_m] and [name_m]Inigo[/name_m] [name_m]Jack[/name_m].
[name_u]Roscoe[/name_u] and [name_m]Rafferty[/name_m] fit best with [name_m]Jack[/name_m]’s energetic feel in my opinion.
I really love [name_m]Peregrine[/name_m] [name_m]Jack[/name_m] and [name_m]Rafferty[/name_m] [name_m]Jack[/name_m]! 
I love [name_m]Peregrine[/name_m] [name_m]Jack[/name_m]! Such an amazing bird and I think the nn [name_u]Perry[/name_u] is fun