Genesis 38:8 And Judah said unto Onan, Go in unto thy brother’s wife, and marry her, and raise up seed to thy brother.
There are several verses and stories around this theme. It seems like maybe it doesn’t fit into anything that we can understand. Apparently the issue is to build your brother’s name. Do something that costs you, does nothing for you but helps your brother be successful.
I think that is the Biblical Christian spirit. Do what you can to build your brother’s name. Help him be a success. Come in under the cover of darkness. Help him and don’t take the credit for it!