Having a singletons after twins. Worried about the youngest one being left out.

I have 18 month old twin boys. They will be 20 months when their baby brother is born. Lately I have been worried about the youngest one feeling left out as they get older. The twins are already referred to as "the twins" by everyone around us so I don't want them to be "the twins and the other one."I don't know if this is a valid fear or not. I could be projecting. I grew up being 10 and 12 years younger than my brother and sister. They were/are best friends and I felt like I grew up as an only child for the most part. Even now they go out and do things together and I never felt that same sibling bond they have with each other. My husband grew up being 18 months younger than his only sibling and they are still very close.I know identical twins often have a strong bond and I want to keep that in my twins but I don't want the younger one to feel like he's just the other one. We might have a 4th but I'm not sure yet. Is this the hormones talking or is this something I have to actively work to prevent? via /r/Parenting http://bit.ly/2F1UusG