[name_m]Bo[/name_m] is my favourite from your list for a potential brother to PJ. I like [name_f]Penelope[/name_f] & [name_m]Bo[/name_m] together too. I don’t mind the different lengths since they have great vibes together. I’m not sure where that would leave you for middle names, however, [name_m]Bo[/name_m] [name_m]Shepherd[/name_m] stands out as far as your list goes.
[name_f]My[/name_f] runner-ups would be [name_m]Montgomery[/name_m] (Monty) and [name_f]Indiana[/name_f] (Indy).
Some suggestions based off your list:
[name_f]Marlowe[/name_f]
[name_m]Jem[/name_m]
[name_m]Sonny[/name_m]
[name_m]Rueben[/name_m] ‘Rue’
[name_m]Iggy[/name_m]
[name_m]Mack[/name_m]
[name_m]Casper[/name_m] ‘Cass’
[name_m]Jethro[/name_m] ‘Jett’
[name_m]Cass[/name_m]
[name_m]Jett[/name_m]
[name_m]Remy[/name_m]
[name_m]Kip[/name_m]
[name_m]Beck[/name_m]
[name_m]Murphy[/name_m]
[name_m]Toby[/name_m]
[name_m]Reggie[/name_m]
[name_m]Joss[/name_m]
[name_m]Turner[/name_m]
[name_m]Louie[/name_m]
[name_m]Radley[/name_m]
[name_m]Arlo[/name_m]
[name_m]Briggs[/name_m]
[name_m]Grady[/name_m] ‘Gray’
[name_m]Wylie[/name_m]
[name_m]Truman[/name_m] ‘Rue’