The couple are set to get married later this year and Nick - who was previously married to Jessica Simpson - revealed "the pressure is on" to catch up to his brother Drew, who has two children.
He told Parade magazine: "I'd like to be a dad sooner than later. I'm getting up there. I've gotta catch up with my brother. [Drew's] got two and I've got zero, so the pressure is on me!"
"I'm at a point in my life where I'm ready to start another chapter. Having kids is a big part of that. I'm excited for what comes next. Life is a Journey, and I'm certainly ready to close this chapter and move on to the next."
Nick, 37, and 30-year-old Vanessa recently threw a cocktail themed wedding shower and now Nick is looking forward to his bachelor party, although he admits he is "fearful".
He explained:"I'm fearful! But we're going to have a great time. At this point in life you don't get to see the boys as much as you used to and a lot of the friends from college and stuff have moved on and have their own families. This is a chance for us all to get together and tie one on and have some fun again. We're all looking forward to it."