There are pros and cons to both single and married status. For example, with kids it's probably better to go married status from a financial point of few cos of school fees, but single status will often get more leave than married status. Down to personal preference I guess, if the company are nice enough to give you the choice.

However, I've not heard of KBR allowing single status people to live off site, and they wont let spouses live on site with you.