I think of them like a cat and a puppy. DD2 is the cat, and DS is the puppy.
If anybody has dealt with these kinds of situations, I'd love to hear about your experiences. I'm struggling with how much to intervene and what exactly to say or do. I have the feeling that this is going to be something we're going to struggle with for a long time.
Edited to add: they're four years old.
Oh my gosh, my heart is breaking with, "Ray ray doesn't love me." My twins are very different from each other, but not in the ways yours seem to be and they have no separate friends. Do you think it would help to sit down with your DS and help him make a list of things he can do with you, his father or his older sister when DD2 wants her space? I'd probably be talking to him a lot about how DD2 needs time by herself from time to time, trying to help him see it wasn't just him she wanted space from, but everyone and part of how she feels ready to play with other people. Would he understand the concept of a timer and leaving her alone for half an hour and then coming back to see if she's ready to play with someone else? Could your DH talk to him about how he deals with the differences between the two of you? Maybe he'd feel better about it if he thought, "I'm like Daddy"? I'm sorry, this isn't very helpful. I'm curious to read what others have to say.
Ugh, I have no real time to reply right now but part of the reason I came here is because I wanted to talk about similar issues with my 5-year-olds, and during their 4th year was when I first started to really notice it. Katie is waaaaay more into Lilly and way more sensitive to Lilly's moods, and sometimes it really does break my heart to see how hurt she gets. I'm going to subscribe to this one and try to get back when there's more time. Hugs in the meantime.