My energy after having baby vs hubby’s

I don’t know how I’m making it through each day on the little bit of sleep I’m getting, 3 weeks PP had a C-section and exclusively breastfeeding not to mention we have a three year old with a lot of energy. My husband is home with us on paternity leave, I love it and I kinda hate it lol. Mostly because he’s always tired, he gets a whole nights rest and even wakes up after our toddler sometimes. He tells me if I need something to let him know, yeah I don’t think so he sleeps right through our toddler yelling and our baby crying. I would call out to him what felt like 100 times when we first came home from the hospital for him to get baby out of the crib for me since I’m sleeping in the recliner. By the time I got him up poor baby was having a full melt down. I don’t get it, how is this possible ??? Like how much sleep does he need to be a fully functional human ?