My initial thought is to suggest setting a bedtime routine that you follow like clockwork. Every night, whether your husband is home or not. Ours is pretty basic: showers, PJs, teeth brushed, stories (each child picks out one plus they get a Bible story), everyone goes potty and gets a drink (to avoid excuses for coming out of their rooms), prayers, hugs & kisses, then lights out. The routine starts at 6:30 and ends at 7:00.
Both kids know that they need to stay in their rooms after the door is closed. I've noticed that the days when Kaylin comes out are the days that she actually sleeps during her quiet time. When I hear her playing or reading instead of napping, she goes to sleep easier at night. On days that she naps, I see the light on under her bedroom door, sometimes immediately after we do our bedtime routine, which is honestly fine with me. She reads or plays quietly, then turns the light off and goes to sleep when she's ready.
Does Joshua still nap during the day? That might be the reason he can't settle down at night...too much sleep. Or maybe he's getting over-stimulated too close to bedtime...? Wrestling with his brother or racing around the house when he might benefit from quieter activities after dinner. Another thought is that he's getting hyped up from sugar, like dessert or juice. Those are just off the top of my head.
If you're shaking your head to all of these suggestions, he might just be a night owl. Which is unfortunate if he shares a room with his little brother. I'm currently struggling with that myself. Jason (11 months) rises with the sun every day. In the summer, that was before 5am. Now, it's closer to 6am. Even with room-darkening shades! The good news is that he's learned to hang out in bed until we come in at 7am, no matter what time his internal clock wakes him up. This morning I heard him squealing at 5:45 with the door closed, so I know it woke Ryan up who was just 14 feet away. Jason sleeps in a different room most nights, but this week he's been in with Ryan, who needs to get as much sleep as possible to be on top of his game for school. Honestly, I don't know what to do about it, other than keep the boys separate for a bit longer, for the sake of Ryan being well rested to learn.
Whatever you decide to do, stick with it. I've given in to the fact that I can't make my kids sleep, but I can enforce the "stay in bed" rule. Keep things mellow, lights low, voices down, eliminate the video games (over-stimulation) and avoid trying to "help" him fall asleep. He'll work through this on his own, as long as you set the boundaries and stick to your guns.
As a child who needed my back rubbed/tickled every night, too long into my elementary years (even babysitters had to do it for me to fall asleep) I will tell you to set your kids up for success now. We moved a lot when I was a kid, so I'm sure the new environments were scary at night, plus my mom was a single working parent, so she probably felt guilty/missed me and the extra quality time at night might not have been a big deal at the time. Just think about the habits you want your boys to have later in life and start setting things in motion toward those goals today.
If Joshua is a night owl or potentially doesn't need as much sleep as most kids his age, give him some books to look at quietly with a nightlight nearby, so he doesn't disturb his brother falling asleep. Explain that chatting and giggling aren't allowed, but make a big deal about him getting a little extra awake time because he's older...as long as he can handle the "responsibility" of it. Make sure he understands that that's a non-negotiable, because the little one definitely needs more sleep than his brother. Try enticing him with rewards for successful nights before punishing him for falling short and replay the list of expectations each and every night until it becomes the norm.
I hope this was helpful! If anyone else has ideas or suggestions, please leave a comment for Emily.