The 33-year-old singer, who gave birth to her second child Ace Knute in June, has a 15-month-old daughter Maxwell with her fiance, reported Contactmusic.
"My relationship with Eric has only grown stronger with the additions to our family. I love seeing him as a dad. I feel like I reached a new level of love for him and I didn't think I could love him any more than I did already," Simpson said.
"Becoming a parent is such a unique and profound experience and doing it together has brought us even closer," she added.