Is the name ok or too similar?!

Danielle • 33yo, first time mom and so excited for it all!! Married 10.03.2014 and we are over the moon about our Nov baby boy!
We are only 5 weeks along and have a girl name picked and a possible boy name... I know it's early...
We really love the name Greyson. My husbands brother has a boy named Mason and wonders if that is too close?
I don't think so... What are your thoughts?
I think that Greyson is perfect for us if we have a little boy.