fil problems

ever since we found out were having a girl my fil keeps making jokes that it's a boy like nonstop jokes and it's getting on my nerves. We told him to stop and he did for a little while but now he keeps saying that he's gonna call the baby brad because it's a boy and everyone is telling him to stop and he won't stop. We know from multiple ultrasounds that it's a girl and were happy with our little girl but he's pissing me off saying she's a boy. how do I get him to stop?