That is shameful. Shame on them for daring to believe, daring to act like they get to see their new relative but not her father. It's unbelievably cold, self-centered, and frankly laughable: without the cousin they wouldn't have the baby, and now they want to pretend that what, she was born to the Virgin Mary?
As for the burning in Hell remark, gotta agree with Exelder, there ain't no hell, there ain't no heaven, and wanting these people to burn in hell is little different than these people wanting the cousin to die at Armageddon for banging his girlfriend in a hotel room 20 years ago.