坊や
ぼうや · bouya · JLPT N2 · noun
male child
坊 (young boy) + や (fond suffix) = little boy, like 'bow' + 'ya' said affectionately
Often used for another family's young son. The や ending adds a warm, familiar tone, so it sounds gentler than 男の子 (otokonoko), the plain word for boy.