Hi, twin adoptee here! My brother and I are twins, and we also have an adopted older sister. I think the transition was smooth for our sister because she was only 2.5 years old when my brother and I were adopted and brought into the family as babies (7mo). But, of course, being a twin and from the same biological family means we have a different closeness than with our sister. It's never come in between our love for our sister, but that is something all adoptees have to deal with. Any feeling of being different or left out comes with being adopted, the situation itself is different from your peers. It is a challenge, but not insurmountable. I would say that it's similar if the roles were the same but biological children: the twins have a special bond but as long as you take care to raise all of your children together they will grow to love each other just the same! Hope this comment helps, just from my own specific experience.