We have a [name_m]Henry[/name_m] [name_m]Knox[/name_m] & fell in love with the name [name_m]Griffin[/name_m]… [name_m]Just[/name_m] need a middle name! Our last name is Underwood, and i think I like the sound of 2-1-3 syllable combination. Any ideas?! 
Griffin Kale Underwood
Griffin Ford Underwood
Griffin Sloane Underwood
Griffin Hayes Underwood
Griffin Lorne Underwood
Griffin Bronze Underwood
Griffin Nils Underwood
Griffin Scott Underwood
Griffin Bjorn Underwood
Griffin Ace Underwood
Griffin James Underwood
Griffin Wes or West Underwood
Griffin Blair Underwood
[name_m]Griffin[/name_m] [name_u]Rex[/name_u]
[name_m]Griffin[/name_m] [name_u]Pax[/name_u]
[name_m]Griffin[/name_m] [name_m]Cole[/name_m]
[name_m]Griffin[/name_m] [name_u]Jude[/name_u]
[name_m]Griffin[/name_m] [name_m]Nash[/name_m]
[name_m]Griffin[/name_m] [name_m]Rhett[/name_m]
[name_u]Love[/name_u] [name_m]Ford[/name_m]! And [name_m]Hayes[/name_m], and [name_m]Ace[/name_m] 
[name_m]Nash[/name_m] is another name I love!
You definitely caught on to the “x” like [name_m]Knox[/name_m], does [name_u]Max[/name_u] flow it it?
[name_m]Griffin[/name_m] [name_u]Max[/name_u] Underwood
What about these?
[name_m]Griffin[/name_m] [name_m]Paul[/name_m] U.
[name_m]Griffin[/name_m] [name_m]Jack[/name_m] U.
[name_m]Griffin[/name_m] [name_m]Scott[/name_m] U.
[name_m]Griffin[/name_m] [name_m]Burke[/name_m] U.
[name_m]Griffin[/name_m] [name_u]Blake[/name_u] U.
[name_m]Griffin[/name_m] [name_u]Bryce[/name_u] U.
[name_m]Griffin[/name_m] [name_m]Brooks[/name_m] U.
[name_m]Griffin[/name_m] [name_m]Hawk[/name_m] U.
[name_m]Griffin[/name_m] [name_u]Meade[/name_u] U.
[name_m]Griffin[/name_m] [name_m]Ross[/name_m] U.
[name_m]Griffin[/name_m] [name_m]Hale[/name_m]
[name_m]Griffin[/name_m] [name_m]Hart[/name_m]
[name_m]Griffin[/name_m] [name_m]Knight[/name_m]
I love [name_m]Griffin[/name_m]!
[name_m]Griffin[/name_m] [name_u]Reid[/name_u]
[name_m]Griffin[/name_m] [name_u]Rhys[/name_u]
[name_m]Griffin[/name_m] [name_u]James[/name_u]
[name_m]Griffin[/name_m] [name_m]Cole[/name_m]
[name_m]Griffin[/name_m] [name_u]Beau[/name_u]
I had a feeling when making my list, based on your son [name_m]Henry[/name_m] Knox, that [name_m]Ford[/name_m], [name_m]Hayes[/name_m], and [name_m]Ace[/name_m] would all be hits! ([name_m]Ford[/name_m] is my personal fave in this case.)
And you could definitely get away with [name_m]Griffin[/name_m] [name_u]Max[/name_u] if you wanted to have an -x ending for both boys. There’s also [name_u]Lex[/name_u], [name_m]Dax[/name_m], [name_m]Bronx[/name_m], [name_m]Jax[/name_m], and [name_m]Tex[/name_m].
[name_m]Griffin[/name_m] Bronze Underwood is cute! Also like [name_m]Griffin[/name_m] [name_m]Nash[/name_m], [name_m]Griffin[/name_m] [name_m]Ace[/name_m], [name_m]Griffin[/name_m] [name_m]Hayes[/name_m] & [name_m]Griffin[/name_m] [name_u]Beau[/name_u].
My ideas are only 2-3 syllabes: [name_m]Griffin[/name_m] Elinox & [name_m]Griffin[/name_m] [name_u]Elliott[/name_u].
But maybe [name_m]Griffin[/name_m] Elix?
[name_m]Griffin[/name_m] [name_m]Felix[/name_m]
[name_m]Griffin[/name_m] [name_m]Luke[/name_m]
[name_m]Griffin[/name_m] [name_m]Lynx[/name_m]
[name_m]Griffin[/name_m] [name_m]Atlas[/name_m]
[name_m]Griffin[/name_m] [name_m]Ezra[/name_m]
[name_m]Griffin[/name_m] [name_m]Leon[/name_m]
[name_m]Griffin[/name_m] [name_u]Tate[/name_u]
[name_m]Griffin[/name_m] [name_m]Rocco[/name_m]
[name_m]Griffin[/name_m] [name_u]Blaise[/name_u]
[name_m]Griffin[/name_m] [name_u]Cruz[/name_u]
[name_m]Griffin[/name_m] [name_m]Judd[/name_m]
[name_m]Griffin[/name_m] [name_u]Phoenix[/name_u]
[name_m]Griffin[/name_m] [name_m]Atlas[/name_m]
[name_m]Griffin[/name_m] [name_u]Onyx[/name_u]
[name_m]Griffin[/name_m] [name_u]Zion[/name_u]