Brother-in-law — a polite term for one's spouse's older brother or an older sister's husband.
お義兄さんが週末に家に来るそうだ。
My brother-in-law is coming over this weekend.
彼のお義兄さんは海外で働いている。
His brother-in-law works overseas.
結婚式でお義兄さんがスピーチをした。
The brother-in-law gave a speech at the wedding.
An older stepbrother or adopted/otherwise non-blood-related older brother; someone regarded as an older brother through family ties.
父の再婚でお義兄さんができたが、年が近くて仲がいい。
My father remarried and I got a stepbrother, and we're close in age and get along well.
兄弟とは違うが、お義兄さんとして家族に受け入れられた。
Although not a biological brother, he was accepted by the family as a brother-in-law/stepbrother.