Sofia Vergara and Nick Loeb split up because she "refused" to have children.
The former couple are currently embroiled in a legal battle over the fate of two embryos they created in 2013 and the businessman says he was always more keen on having kids than the 'Modern Family' star, who has a son Manolo, 22, from a previous relationship.
Nick said: "When we got engaged, in 2012, I began to push for children. As I said in my complaint, my fiancée insisted that we use a surrogate. With her eggs and my sperm we created two female embryos. The first embryo we implanted didn't take. The second time, the surrogate miscarried, and I felt crushed.
"A year later, we tried again, creating two more embryos, both female. But as we began to discuss other potential surrogates, it became clear once more that parenthood was much less urgent for her than it was for me.
"We had been together for over four years. As I was coming on 40, I gave her an ultimatum. When she refused, we split up."
The 39-year-old businessman has offered to "pay all expenses" to have a surrogate carry the embryos, but his former fiancee - who is now engaged to Joe Manganiello - has refused.
He added in a piece for the New York Times newspaper: "I asked her to let me have the embryos, offering to pay for all expenses to carry our girls to term and raise them. If she did not wish to share custody, I would take on full parenting responsibilities and agree to have her declared an egg donor.
"She has refused...
"I take the responsibility and obligation of being a parent very seriously. This is not just about saving lives; it is also about being pro-parent."
Sofia's lawyer Fred Silberberg recently stated the 42-year-old star "has never wanted to destroy her embryos".
He added: "[Sofia] has always maintained that they be kept frozen, a fact of which Loeb and his counsel have always been aware, despite Loeb's statements to the contrary."