And then there were 3… which sounds best in his full name? We’ve decided to use [name_m]Parkin[/name_m] as his middle name, we just think it’s a nice subtle way to honor my husband’s family.
I’d suggest [name_m]Theodore[/name_m] as the longer version of “[name_u]Theo[/name_u].” Otherwise, it’s super cute!
We aren’t huge fans of [name_m]Theodore[/name_m] it feels kind of stuffy and we prefer a more relaxed vibe.
Understood! [name_u]Theo[/name_u] is a great choice 
I love [name_u]Everett[/name_u]!!
Theo is my favorite boy name, so that’s what I voted for. I think it flows nicely with [name_m]Parkin[/name_m]!
However, I think [name_u]Everett[/name_u] & [name_u]Callum[/name_u] are also lovely options, so you really can’t go wrong! Maybe you could take all three with you and choose which one suits him more!
also, so glad to see you went with [name_m]Parkin[/name_m]! 
While [name_u]Everett[/name_u] and [name_u]Callum[/name_u] are great, there’s just something about [name_u]Theo[/name_u] [name_m]Parkin[/name_m]. 
It sounds charmingly boyish and adventurous to me.
Completely agree with @regionlatbest though - you can’t go wrong with any of these!
Theo sounds the best with the flow but they are all great combos
I love [name_u]Callum[/name_u] nicknames [name_u]Cal[/name_u] !!!
I couldn’t pick these are all great choices. Good luck!