I think ...; maybe ...
そんなに心配しなくても大丈夫なんじゃないかな。
You probably don't need to worry that much.
トムが言ったことは嘘なんじゃないかな。
I think what Tom said might have been a lie.
トムのお父さんは弁護士なんじゃないかな。
I think Tom's father might be a lawyer.