My emotions are out of control

I am at thanksgiving and my cousin who still lives at home just gave birth to her second kid with her boyfriend. None of my family knows that we have been ttc for the last 7 months. They unknowingly ask me to hold the new baby, or if I glance over at her I start crying 😭. How do you keep your emotions in check during this holiday season with seeing family/babies in person. Sincerely—Emotional wreck