And for a while, yes, the family will simply have to endure it until Mikey grows out of the stage of screaming on the same high pitch for minutes on end and crying, crying, crying because he's not getting his way.
Which is why my family's cousin did. And yes, we sat there while he screamed and cried for easily 15 minutes while his parents turned their backs and had lighthearted conversations with the rest of us.
Mikey is our family member too--him learning how to control himself, etc., is our burden as well as his parents' burden. We're part of his family; he belongs to us. We have a stake in how he grows up. If enduring this for a while each get-together until he grows out of it is the price we pay for being connected to him and the rest of his family.
Mikey's PARENTS are our family members, and supporting them while they dealt with this unexpected and difficult and embarrassing reaction on the part of their little kid was what we did because they deserve our support; they belong to us.
Nobody promised me a completely stress-free family experience. I don't expect it.
(Though I will say--this really did interfere with the larger family bonding. We had a hard time feeling connected to him. Of course, it didn't help that when he got older, like 6 to 12, he didn't particularly care to speak to any of us. But we might have created a different dynamic if we hadn't spent 9 months being sort of irritated at him and feeling that he was a slightly inhuman being.)