To make this short, I'm triggered that at my dad's house we're 5. At my mom's house it's just her, my brother and me. It's not a problem if I lay the table for 4 people or, even better, if my mom's boyfriend comes over. But here it's my dad, my brother, my stepbrother, my dad's girlfriend and me. I can't just remove a seat or plate. What should I do?

For context, I have OCD traits and I have an obsession with 4 and its multiples but it's not a disorder because it's not affecting my life that much