First off, it sounds like your son has developed a sleep association with being held until he falls asleep. The only way to do this is to help him learn to fall asleep under another set of circumstances. Think of what happens if you fall asleep on the couch, all of a sudden you wake up and you're on the bathroom floor- wouldn't you cry too? The best way to help him is to give him the opportunity to learn to fall asleep in his crib- then when he wakes up in the middle of the night- in his crib where he initially fell asleep - he will roll over, go back to sleep since everything is "where he left it".
The controlled crying it out would be an excellent way to help you accomplish this. This provides reassurance to your child that you haven't left and are there for him if he needs it, and to you as well- so you can see that he is not physically in any harm's way. Complete your bedtime routine as normal- except the part where you let him fall asleep on you or your husband. Instead of that happening, hold him for a minute or two to give him a last minute cuddle- then lay him down in his crib, sleepy but awake. You can tell him "goodnight" or "it's time to sleep". Then leave the room as usual. He'll most likely get up and cry- so after 5 minutes or so, come in, do not touch him or move him, and tell him "sorry- but it's time to sleep", and leave the room again. He'll probably get really mad and cry harder. Wait 10 minutes of solid crying until the next time you check, and then 15 minutes until the next time. Continue to do this at the 15 minute interval for the first night until he finally falls asleep on his own. If at any time you suspect he has a genuine need, like a dirty diaper, by all means take him out and change him- but keep things short and businesslike so he knows that this is the time he's supposed to be sleeping.
The next night- repeat the same thing, only start at 10 for the first check, then 15, then 20. And continue at 20 minutes until he falls asleep on his own. To be honest, this may take up to a week to work (although it only took 2 days with my son, and 3 days with my daughter)- so try and start it at a time that might be a little more convenient for your family (like over a weekend). When I did this with my daughter, she cried for 2 1/2 hours the first night, one hour the next, and then 1/2 hour the third night- and we've never had a problem since.
If your older son wakes up at any time, you can just reassure him that it's okay- and that his little brother is learning how to sleep on his own. He also will adjust to the crying, and will most likely go back to sleep once he knows what's going on, or once your younger son falls asleep. If you want him to share a room with his sibling, then you should leave him be and keep him in that room- because he honestly will have to be used to noises of his younger sibling if he's to sleep in that environment.
It is harder to do the older they get, so I suggest doing it as soon as possible- because once he gets to be 2 years old, his bad habit will be very entrenched and a lot harder to break.