He is 60 years old. They got married in 1980, which makes it likely that she is at least in her mid-50s. (I was 14 in 1980; I am 51 now.) At this point, she doesn't have "infertility": she has "post-menopause."
His children were born 8 years ago, when his wife was probably in her late 40s. Very few women, no matter how healthy, naturally have children after age 45.
Seeking to hire a uterus at this point in his and his wife's life is WEIRD.
Shall I go full tinfoil chapeau? How do we know those kids are the result of a surrogacy agreement and not the result of a hook up/affair?
Maybe their marriage is in trouble, and this (raising another child) is one thing they haven’t tried yet.