I couldn't agree more with mermaid33 and bzl.
Your first obligation is to your children, who just went through a life-altering experience. Don't dump another one on them by creating a baby with your rebound boyfriend so that you have little time to devote to them.
And seriously, he wants a kid for his ESTATE? Is he an 18th century baron? The problem for most people is setting aside enough money for their kids they have, not creating kids so they have something to do with their money. Believe me, there are enough children in this world who could benefit from that estate--you know, by getting dewormed, having some protein for the first time in three months, getting inoculated against disease, being treated for HIV--that this guy doesn't need to do the world a favor by creating an heir for the sake of creating an heir. That is one of the most revoltingly selfish and weirdly unethical things I've heard in a while.
Please do not reproduce with not-so-little Lord Fauntleroy. If he is that bizarrely selfish prior to having you birth his child emperor, I can only imagine how he'll react when you give attention to the 10 year old instead of the heir apparent.