What are some boys’ names that work in both French and Russian? [name]Just[/name] brainstorming here. 
ETA: Also, it would help if you could include French and Russian nicknames that would be used. Thanks!
[name]Leo[/name]? That’s the only one I can think of off-hand. I’m much more familiar with French than Russian, but I believe [name]Leo[/name]'s usable in both places. [name]Leo[/name] Tolstoy’s a famous Russian bearer, and last time I checked, [name]Leo[/name] was in the current French top 20.
Possibly something like [name]Jonas[/name], too, although it would be pronounced differently–I know the Polish variant, Jonasz, is in use, so I would guess it could be used in [name]Russia[/name], and my best friend (who was from [name]Paris[/name] and had her triplets in [name]Paris[/name]) has a son with the name [name]Jonas[/name]. I’m not sure it’s exactly popular in either area, though.
Other options:
[name]Andre[/name] (French)/[name]Andrei[/name] (Russian)
[name]Alexandre[/name] (French)/[name]Alexander[/name]/[name]Aleksandr[/name] (Russian)
[name]David[/name] (in both French and Russian, both pronounced dah-VEED, from what I understand)
[name]Peter[/name] (well, in French it’d be [name]Pierre[/name], or the diminutive, [name]Pierrot[/name], and in Russian it would be [name]Pyotr[/name])
[name]Edward[/name] (the French spelling is [name]Edouard[/name]; I’m not sure about how it would be spelled in Russian with the English alphabet…)
[name]Julian[/name] (spelled [name]Julien[/name] in French; Yulian in Russian, it looks like)
Those were the popular ones I’ve found–if you want one that keeps the same spelling for both nationalities, I think [name]Leo[/name] is probably your best bet. 
Good luck!
ETA: I’m honestly not sure about nns. If you went with [name]Peter[/name]/[name]Pierre[/name], [name]Pierrot[/name] would be the French diminutive. From my knowledge of the French, they don’t use a ton of nicknames. As far as I know, my friend never used a nn for [name]Jonas[/name]… and most of the classics are fairly short. She knew a [name]Julien[/name] who was always [name]Julien[/name], too. I am less familiar with Russian nns–I know there’s [name]Sasha[/name]/[name]Sascha[/name] for [name]Alexander[/name], but other than that, I have no clue. [name]Mischa[/name]/[name]Misha[/name] for [name]Mikhail[/name], and I’ve heard [name]Pasha[/name], too–but I have no clue what that’s supposed to be the nn for.
Thanks, [name]Ash[/name]. I’m brainstorming for a character who has a French mother and a Russian father. He’ll have the French form of the name I choose. Right now I think it’s between [name]Alexandre[/name] and [name]Nicolas[/name]. Dad would call him [name]Sasha[/name] or [name]Kolya[/name]. Middle name possibilities (again, all French) are [name]Edouard[/name], [name]Emilien[/name], [name]Etienne[/name], [name]Julien[/name], and [name]Raphael[/name].
[name]Leon[/name] was my first thought
[name]Just[/name] adding to what ashthedreamer said, [name]Pasha[/name] is a nickname for [name]Pavel[/name] I believe.
lol, that makes more sense! I was thinking [name]Patrick[/name] and I just knew that couldn’t be right…
Yep. [name]Pasha[/name] is a nickname for [name]Pavel[/name] which is the Russian form of [name]Paul[/name]. I had no clue about French and Russian names prior to this, so it’s been fun.
I had a french foreign exchange student friend back in undergrad named [name]Nikolai[/name]. I know that this is also a Russian name. I am not sure if [name]Nikolai[/name] is traditionally french or not–although I know [name]Nicholas[/name] is used more often in [name]France[/name].
[name]Nicolas[/name] and [name]Nikolai[/name] are pronounced nearly the same. According to Behind the Name, [name]Nicolas[/name] is nee-ko-LAH and [name]Nikolai[/name] is nee-ko-LIE.
I’ve decided on [name]Nicolas[/name] (nee-ko-LAH) for this character. Any thoughts on these combos?
[name]Nicolas[/name] [name]Edouard[/name] (ay-DWAHR)
[name]Nicolas[/name] [name]Etienne[/name] (ay-TYEN)
[name]Nicolas[/name] [name]Julien[/name] (zhoo-lee-AWN)
[name]Nicolas[/name] [name]Raphael[/name] (ra-fa-[name]EL[/name])
For me, it’d be between [name]Nicolas[/name] [name]Edouard[/name] and [name]Nicolas[/name] [name]Etienne[/name]. [name]Both[/name] have good sound and flow. I’m leaning a little more toward [name]Edouard[/name] as the middle, just because the French and Russian versions of [name]Edward[/name] look more similar, as far as I can tell with a bit of limited research, than the French and Russian versions of [name]Stephen[/name].
Best of luck!
[name]Xavier[/name] was always my favorite French boy name
[name]Antoine[/name] is a second.
Thanks everyone!