The 98 Degrees star wed Simpson in 2002, but they split in 2005 after just three years of marriage.
Both singers have since moved on, and Lachey confesses having a baby with the blonde beauty would have made their relationship, which was documented on MTV reality show Newlyweds, all the more complicated.
During a candid interview on Jenny MCCarthy's Dirty, Sexy, Funny satellite radio show, he said, "In our situation, that was probably the best thing that could have ever happened that we didn't have kids. And look, you're always going to love your kids no matter how you feel about their other parent, but all things being equal, it was the best thing probably for both of us that we went on with our lives."
Lachey has since settled down with his second wife, Tv personality Vanessa, who is pregnant with their second child, while Simpson has also moved on and is now a mum to daughter Maxwell, two, and son Ace, 16 months, with her new husband, former American footballer Eric Johnson.
He continued, "She's obviously happily married with two (kids) and I'm happily married and about to have two so it all worked out the way it was kind of meant to work out."
And Lachey reveals the former couple, which divorced in 2006, has not been in touch since.
He added, "She and I don't necessarily stay in each others lives. I wouldn't say it's friends and I wouldn't say it's enemies - there is just no contact. We both moved on with our lives... it's not animosity, it's not friendship, it's just kind of nothing."