Jessica (left) and Ashlee Simpson
05/01/2012 at 10:30 PM EDT
Just hours after Jessica Simpson
gave birth to daughter Maxwell Drew
, her sister Ashlee Simpson
says she's smitten with the newest family member.
"Bronx and I are in love with Maxwell already!" Ashlee, who is mom to 3-year-old son Bronx, tells PEOPLE exclusively. "Jessica has wanted to be a mom since we were little girls and I couldn't be more excited for her and Eric!"
Ashlee has already begun spoiling her niece: In March, she gifted her with a tiny Fendi dress and matching garment bag while celebrating the impending birth at Jessica's Charlotte's Web-themed baby shower
"Ever since Ashlee had Bronx
, we've become closer and closer," Jessica told PEOPLE at the time. "I'm glad that our babies are just going to be three years apart."
So is Bronx, who can't wait to have a little playmate.
"He records songs on my sister's iPhone about the things he wants to do with the baby, like swim in the ocean and go to the playground," Jessica said. "The first one just made me cry. We're making a CD of them – it was the best gift of all."
That is, until now.