Getting baby to actually fall asleep around toddler


My son is 3 and I’m having trouble getting the baby to fall asleep around him. I take her in her room and turn the box fan on loud and start feeding and rocking her but my toddler always comes in screaming and playing.I try to entertain him with stuff while I’m trying to get her down but nothing works...

I would let her sleep in her room alone with white noise but it’s just getting her to fall asleep around him to begin with that’s the hard part 😭