Hello my dear @wendyth16, I wish you had that option to live the beautiful feeling of being a mother for a day and to share with him all that love and infinite love that you have treasured in your heart.
Perhaps my words are not of great encouragement to your life and I do not know your situation, but what I can tell you is that you continue to share your love with your nephews or maybe God has something in store for you, children can also be born from our hearts, even if they are not initially formed in our womb.
I send you a big hug my friend