Talk to the parents. Tell them what is happening, ask to discontinue allowing the child to sleep in their bed, etc...

Op here: so what would be some good ideas for me to use to get them both to nap?

Weekends MB probably naps with the baby too...

Recently my charge has been allowed to sleep in mb/DBS bed because MB has been traveling. This means when I put her in her crib for nap she's good for a few minutes and then she looses it and wakes her brother. She is 2 and her brother is 1, they have had maybe a half an hour nap per day... Which not only is making them wxhausted but me incredibly frustrated come naptime. I want to say something but I obviously am not the parent. I'm hoping she acts the same over the weekend and her parents put an end to this nonsense because I'm seriously loosing my mind.

Ugh.