for baby portrait i will suggest canon or fuji or sony,
shoot baby you cant use flash so iso noise control very important,
m43 n nikon j personally dont recommend at all,
some samples for u..... http://www.baby-kingdom.com/forum.php?mod=viewthread&tid=5434094
for you i suggest nex 6 kit + 50 1.8 (10k) / fuji xe1 + 35 1.4 (10k)
dont buy full frame if this is your first time using dslr,
step by step is the best, good luck~