I have an older brother who is only a year older than me, and I have a younger sister who is three years younger than me. We have always gotten along well.
My brother and I were born within one year of one another, but my sister is three years younger than me. We've always been like best friends.
ーI have an older brother who is only a year older than me, and I have a younger sister who is three years younger than me. We have always gotten along well.
「一つ年上の兄と3つ下の妹がいて、昔から仲が良いです」
an older brother who is only a year older than me で「私より1つ上の兄」
a younger sister who is three years younger than me で「私より3つ下の妹」
to get along well で「仲良くやる・気が合う」
ーMy brother and I were born within one year of one another, but my sister is three years younger than me. We've always been like best friends.
「兄と私は年子だが、妹は3つ年下です。私たちは昔から仲が良い」
My brother and I were born within one year of one another で「兄と私はお互い１年のうちに生まれた」＝「兄と私は年子です」
We've always been like best friends. で「私たちは昔から親友のようです」
ご参考まで！
I have an older brother who is one year older than me and a younger sister who is three years younger than me, and we’ve always been very close.
I have an older brother who is one year older than me and a younger sister who is three years younger than me, and we’ve always been very close.
My brother and I are only one year apart, and I also have a younger sister who is three years younger than me. We’ve been very close since we were kids."
まず「年子」は、日本語ではよく使いますが、英語で一語でぴったり同じように言うより、
one year older than me（私より1歳上）
one year apart（1歳違い）
のように説明するのが自然です。
カナダ 
アメリカ合衆国 
