Our older daughter is quite mature for her age, but her younger brother is another story. He doesn't put much effort into anything.
I'm worried about my son because he does everything so half-heartedly compared to his older sister who really has her act together.
ーOur older daughter is quite mature for her age, but her younger brother is another story. He doesn't put much effort into anything.
「うちの娘は年齢の割にしっかりしているけど、彼女の弟は全く別の話。彼は何にも努力しない。」
be mature for one's age で「年の割にしっかりしている」
another story で「別の話・また話が違う」
put effort into ... で「…に力を入れる・努力する」
ーI'm worried about my son because he does everything so half-heartedly compared to his older sister who really has her act together.
「息子はしっかりしたお姉ちゃんに比べて、なんでも中途半端なので心配です。」
I'm worried about ... で「…が心配です」
half-heartedly 「本腰を入れないで」
have one's act together で「しっかりする・きちんと行動する」
ご参考まで！
カナダ 
