Is he serious about marriage? Guys advice, please?

My boyfriend & I talk about getting married quite frequently. I love when he brings it up :) but how do I know he is serious about it? He says things like he doesn't want to not be without me ever and that I'm his best friend and he would tell things to me before he would tell any of his guy friends. One night he even wanted to come up with names for our kids and we couldn't get off the phone til we agreed on them.

Do most guys do this?