My husband and I have always struggled coming up with names we both like. We do try and hit the sweet spot of familiar but not too popular. Our current boys are [name_u]Elliott[/name_u] and [name_m]Oliver[/name_m] (yes, [name_m]Oliver[/name_m] is popular now, but it wasn’t quite so much when we named him). Our last name is only one syllable, so we’d rather go with a 2 or 3 syllable name. Since he’s due at [name_u]Christmas[/name_u] time, some tie in to that would be cool, but certainly not a necessity. Any suggestions on what sounds good with his brothers?
Maybe [name_u]Noel[/name_u]? [name_u]Elliott[/name_u], [name_m]Oliver[/name_m] and [name_u]Noel[/name_u]
Other suggestions for a [name_u]Christmas[/name_u] baby: [name_m]Caspar[/name_m], [name_m]Shepherd[/name_m], [name_m]Nicholas[/name_m], [name_m]Felix[/name_m] !
I really like [name_u]Elliott[/name_u], [name_m]Oliver[/name_m] and [name_m]Felix[/name_m]
[name_m]Gabriel[/name_m] or [name_m]Jack[/name_m] (as in [name_m]Jack[/name_m] [name_u]Frost[/name_u])
[name_m]Gabriel[/name_m] would fit well with your other boys. You can also call him [name_m]Gabe[/name_m].
Personally I like [name_m]Jack[/name_m], though it isn’t 2 syllables. It’s one of those short and sweet type of names that still has substance.
What about these?
[name_u]Elliot[/name_u], [name_m]Oliver[/name_m], and
[name_u]Noah[/name_u]
[name_m]Asher[/name_m]
[name_m]Silas[/name_m]
[name_m]Colton[/name_m]
[name_m]Gabriel[/name_m]
[name_m]Joseph[/name_m]
[name_m]Levi[/name_m]
[name_m]Simon[/name_m]
Our son was born on [name_u]Christmas[/name_u] [name_f]Eve[/name_f]. We went with [name_u]Dillon[/name_u], meaning faithful.
[name_u]Noel[/name_u] (oldie but goodie) or [name_u]Noah[/name_u] if you want something a little less obvious, [name_m]Winston[/name_m] (sounds like [name_u]Winter[/name_u] a bit), any angel name would work well (i.e. [name_m]Gabriel[/name_m], [name_u]Michael[/name_u]), [name_m]Casper[/name_m], [name_m]Nicolas[/name_m]/[name_m]Nicholas[/name_m], [name_m]Christian[/name_m]. In terms of names that just go well with your sons, my first thought was [name_m]Daniel[/name_m]. [name_f]Hope[/name_f] any of these are good for you! 
[name_m]Nathaniel[/name_m] or [name_m]Nathan[/name_m] (nn. [name_m]Nate[/name_m]?) means “gift of God,” and with the nat- root, it reminds me of [name_f]Natalie[/name_f], a [name_u]Christmas[/name_u] name. Others:
[name_u]Douglas[/name_u] (as in [name_u]Douglas[/name_u] fir)
[name_m]Clarence[/name_m] (as in It’s a Wonderful Life)
And I’ll second [name_m]Felix[/name_m] and [name_m]Gabriel[/name_m] as suggested above.
[name_m]Gabriel[/name_m], [name_m]Nathan[/name_m], or [name_m]Nicholas[/name_m] would be my suggestions 
Absolutely love the suggestion of [name_u]Elliot[/name_u], [name_m]Oliver[/name_m] and [name_m]Felix[/name_m]!! (Although [name_m]Felix[/name_m] doesn’t have a [name_u]Christmas[/name_u] vibe it flows so well with your two sons names)
[name_m]Immanuel[/name_m] or [name_m]Imanuel[/name_m], [name_u]Angel[/name_u] (pair this with a very masculine middle name)ex.[name_u]Angel[/name_u] [name_m]Christopher[/name_m], [name_f]Ivey[/name_f],(pair this one also with very masculine name),[name_m]Ulysses[/name_m], [name_m]Isom[/name_m], [name_m]Alec[/name_m], [name_m]Angelo[/name_m], [name_m]Aldwin[/name_m], [name_u]Arlo[/name_u], [name_m]Ancel[/name_m] or[name_m]Ansel[/name_m], Alder, [name_m]Axel[/name_m], [name_u]Alden[/name_u] or Aulden, [name_f]Ansley[/name_f],
I really like [name_m]Nicholas[/name_m] with [name_u]Elliot[/name_u] and [name_m]Oliver[/name_m] as it has 3 syllables and shares the L and O sounds. It also has a great [name_u]Christmas[/name_u] tie.
[name_m]Joseph[/name_m] is another excellent choice with a [name_u]Christmas[/name_u] tie in.
I also like [name_u]Paxton[/name_u] (peace) if you want something different.
[name_m]Jasper[/name_m], the name of one of the wise men
[name_m]Felix[/name_m] (means happy and its a happy season)
[name_u]Elliott[/name_u], [name_m]Oliver[/name_m], and [name_m]Adrian[/name_m]
[name_u]Elliott[/name_u], [name_m]Oliver[/name_m], and [name_m]Douglas[/name_m]
[name_u]Elliott[/name_u], [name_m]Oliver[/name_m], and [name_m]Felix[/name_m]
[name_u]Elliott[/name_u], [name_m]Oliver[/name_m], and [name_m]Montgomery[/name_m] “[name_m]Monty[/name_m]”
[name_u]Elliott[/name_u], [name_m]Oliver[/name_m], and [name_m]Ramsey[/name_m]
[name_u]Elliott[/name_u], [name_m]Oliver[/name_m], and [name_m]Travis[/name_m]
[name_u]Elliott[/name_u], [name_m]Oliver[/name_m], and [name_m]Wesley[/name_m]