The comment can be edited if the post is edited.

This is the thing. OP is being asked to allow others to be mislead. You could argue that it's an insignificant thing, but if it's so insignificant why should it not be able to bear being corrected?

If Auntie and Cousin want it to lay right, they should edit the post or reply with grace: "I can't believe I wasn't thinking about that! Congrats to you and your bro too, it's so great to see this generation making such great strides..." or whatever.

Point is, if they don't want to look like they're lying, there are easy was to do that like (1) don't lie, (2) if you get caught in error, correct the error. There is no (3) if you love me let me lie.