Your question is an interesting one, and, as you know, one that the Bible does not address directly. Questions of this kind should always consider principles and precepts found in the Scriptures.
I do not believe it is an accident that you have written me asking for help in finding an answer. I am the father of two adopted children. My wife and I could not conceive our own “biological” children. We wrestled with this question ourselves a number of years ago. Our children are now 25 & 23. There are many “ethical” questions one may encounter about a surrogate mother and her relationship to her child, and to the family, and to her “biological” mate, and the child’s relationship to her, etc., etc.
There are NO “ethical” questions about adoption.
James 1:27 says:
“Pure and undefiled religion in the sight of our God and Father is this: to visit orphans and widows in their distress, and to keep oneself unstained by the world.”
There are thousands of children in our country who need a loving family and home. Although the adoption process is cumbersome, and at times extremely difficult, it (in my experience) is worth the time and effort. I would encourage you to consider adoption.