Eh, I don’t know. I married at 27 and my gorgeous, adorable younger brother stayed single. He was living in the country, where there are few single women, and working in a guy-dominated field while he took care of our aging parents. He finally got married at 43 when the folks had passed. He and his wife have been SO HAPPY. Fortunately she knows that she is the luckiest woman in the world, he worships her, and they have a wonderful life together. She’s God’s reward to him for being so good and faithful. It’s only a disappointment to them that they were too old to start a family. But they were not freaks, and their marriage is a lot happier than mine was. They just didn’t meet the right people.
There are always exceptions to general rules; and great for your brother
Your brother and his wife could adopt. We had two of our own and adopted two more.