We just found out we’re expecting - yay! It’s too early to know the gender, but I’m wondering what other berries would name a brother to [name_f]Fiona[/name_f] [name_f]Mae[/name_f]? I listed some favorites below, but please feel free to think outside of those names and add middles 
We don’t like super common names, and here are some of our girl/boy favorites -
Girls: [name_f]Lorelei[/name_f], [name_f]Petra[/name_f], [name_u]Rory[/name_u], [name_f]Tamsin[/name_f], [name_f]Pippa[/name_f]
Boys: [name_m]Lachlan[/name_m] “[name_m]Lock[/name_m]”, [name_m]Declan[/name_m] (seems to be getting popular), [name_m]Cormac[/name_m], [name_m]Rupert[/name_m], Jack (also seems popular?)
I love the combo [name_f]Fiona[/name_f] [name_f]Mae[/name_f]! It’s pretty and short,and undeniably spunky! I think the four boys’ names you’ve listed all go incredibly well with your daughter’s name. Here are a few other names I think could work:
[name_m]Lorcan[/name_m]
[name_m]Conal[/name_m]
[name_m]Oscar[/name_m]
[name_m]Dominic[/name_m]
[name_m]Walter[/name_m]
[name_m]Nicholas[/name_m]
Oisín
[name_m]Gideon[/name_m]
[name_m]Joel[/name_m]
Senen/[name_m]Senan[/name_m]
[name_u]Dara[/name_u]/[name_u]Darragh[/name_u]
Dónal
[name_u]Corbin[/name_u]
[name_m]Dalton[/name_m]
[name_m]Bryan[/name_m]
[name_m]Eric[/name_m]
[name_m]Ciaran[/name_m]
[name_m]Frederick[/name_m]
[name_m]Frank[/name_m]/[name_u]Francis[/name_u]
[name_m]Hamish[/name_m]
[name_m]Trenton[/name_m]
As for middles, you could link your daughter’s name and a potential brother’s name together by having another three-syllable first name with a spunky single-syllable middle, such as [name_m]Dominic[/name_m] [name_m]Fox[/name_m] or [name_m]Nicholas[/name_m] [name_u]Dean[/name_u] 
I like all of those names except [name_u]Rory[/name_u] and [name_m]Rupert[/name_m], no offense.
I would go with [name_m]Declan[/name_m] or [name_m]Lachlan[/name_m]. I love those for the boys. I love [name_f]Lorelei[/name_f] and [name_f]Tamsin[/name_f] as well.
[name_u]Love[/name_u] [name_m]Lachlan[/name_m]! Also second the suggestion of [name_m]Lorcan[/name_m] and would like to add [name_u]Larkin[/name_u] as unisex option. Also think [name_u]Rory[/name_u] could work on a boy as well as a girl. [name_f]Fiona[/name_f] and [name_m]Lorcan[/name_m] are my personal favorite.
[name_m]Lachlan[/name_m] is a great name! I like all of the names you suggested, but I think [name_f]Fiona[/name_f] & [name_m]Lachlan[/name_m] and [name_f]Fiona[/name_f] & [name_m]Jack[/name_m] are my favorites - but when you think about it, [name_m]Lock[/name_m] and [name_m]Jack[/name_m] have very similar sounds.
[name_u]Love[/name_u] [name_m]Cormac[/name_m], [name_m]Declan[/name_m] and [name_m]Jack[/name_m] with [name_f]Fiona[/name_f]!
I think all of your boys’ choices go well with [name_f]Fiona[/name_f]. I especially love [name_f]Fiona[/name_f] & [name_m]Lachlan[/name_m] and [name_f]Fiona[/name_f] & [name_m]Jack[/name_m]. [name_m]Jack[/name_m] is much more popular than your other options though, so if this will bother you I probably wouldn’t use it.
One consideration I would make would be whether you plan to have more kids. I think if you went with one of the more Scottish/Irish names the sibset would be very Scottish/Irish and a third sibling would also have to have a Scottish/Irish name or he/she would kind of be the misfit of the group. Your taste in girls names doesn’t seem as distinctly Scottish, so just something to consider.
Some more suggestions you might like:
[name_m]Alistair[/name_m]
[name_m]Archer[/name_m]/[name_m]Archie[/name_m]
[name_m]Atticus[/name_m]
[name_u]Brennan[/name_u]
[name_m]Callum[/name_m]
[name_m]Caspian[/name_m]
[name_m]Cullen[/name_m]
[name_m]Dermot[/name_m]
[name_m]Edison[/name_m]
[name_u]Elliot[/name_u]
[name_m]Evander[/name_m]
[name_u]Everett[/name_u]
[name_m]Felix[/name_m]
[name_m]Graham[/name_m]
[name_m]Hugo[/name_m]
[name_m]Jasper[/name_m]
[name_u]Jude[/name_u]
[name_m]Kellan[/name_m]
[name_u]Kieran[/name_u]
[name_m]Malcolm[/name_m]
[name_m]Otis[/name_m]
[name_m]Otto[/name_m]
[name_m]Ronan[/name_m]
[name_u]Roscoe[/name_u]
[name_m]Seamus[/name_m]
[name_m]Silas[/name_m]
[name_m]Simon[/name_m]
[name_m]Thaddeus[/name_m]
[name_m]Wiley[/name_m]