Older sibling and sleep training

Samantha • Mom of 2! 🎀 4/15/16 💙4/29/18

How do you sleep train with an older sibling!? My 6 month old talks and yells so loud that he’s woken his older sister up before! So now whenever he is yelling i just run in and nurse him back to sleep but right now it’s multiple times per night!

Help!!