Marriage baby

Ok so my husband and I married on April 4th 2015. We already have two children together (5year old girl, and 2 year old boy). Now all we hear is " you guys should have another baby that way you'll have a 'Marriage baby'" 😳😳😳😳 what the heck is a marriage baby?? Are the children we have now not as special because their out of wedlock??? This is the craziest thing I've ever heard, yet so many people have said it to us.