I have posted this before, when DS1 met DS2 he took one look and screamed .
It is similar here - DS1 is a sweetie but DS2 is a charmer. DS2, despite some communication problems, has a huge fan base.
I have gone for the split bedtimes - it has made a real difference. I, also, try to get some time separately with each of them - they do appreciate it.
I'm not surprised your DS1 is feeling sensitive right now; changes can be so hard. The only other idea is can you do something with them together that they both enjoy - I go swimming with mine (it is very hard work at 4 and 2) but it is a real bonding exercise.