I really like both
Misha and
Sasha, and I love
Sasha on a boy. They're adorable for cats too, and because they're short, they're not too confusing for the cats (don't they say that pet names should be one/two syllables or did I dream that?).
I actually think
Misha and
Sasha are adorable together.
But some other ideas are:
Artyom / Artya
DimaFedyaIlyaKirillKolyaKostyaLevMatya
Mitya (
Misha and
Mitya is pretty cute)
Pasha PetyaRuslanShura / Shurik (another form of Aleksandr/Sasha -
Misha and
Shura /
Misha and Shurik are both cute)
TikhonValya
Yasha / Yashik
Yefim /
Fima Yuriy