He might nap differently for you. I watched a baby for a few months when my oldest was a toddler. Somehow, someway, I got them both to nap lol. I forget exactly how, 7 years later, but some combination of nursing for my son, and either before or after rocking, holding, patting the back of the baby worked. I think it'll be possible to get them both to nap, it just might take time to figure out the best way.