What is the sign that swallows settle down under the eaves?

It's hard to say whether it's a good thing for a swallow to settle down under the eaves, but it's just that the swallow thinks it suits his own mind. In the mid-1970s, a nest of swallows came to our neighbor's house. At that time, all the children in our village went to see it, and the children in the village were very happy. It is said that this nest of swallows can bring good luck to his family. Until 2000, this nest of swallows was still there, and many nests of swallows were bred in its home. However, the owner has two sons and two daughters. Two sons are in their fifties and two women are in their forties.