I'm a nanny to a 2 year and 3 year old, as well as their cousin. 2 year old likes the 9 year old better! help.?

I'm a nanny to my baby cousins, but we're close enough to where they call me auntie. i'm 17, the baby girl is 22 months old and the boy is 3 and a half. I will occasionally watch a 9 year old, their other cousin from the other side. The kids love me a lot, they cry when I leave them for the day. BUT, when the 9 year old is over, the baby girl always wants to go to her, and it's frustrating. I feel completely stupid, that a 2 year old wants to go to a 9 year old over me considering i'm their nanny/auntie. What could I do, over this summer to make the baby girl maybe, i don't know... like me more? I want to bond with her better, thinking that will do the trick.... I just feel stupid and ha yeah i'm jealous of a 9 year old. But I watch them all the time... I want to bond with them well. Please help.... Thanks.