Can children sense "genes" or family?

I am not sure if this is the right sub but this is something going through my mind a lot. I am the oldest in my generation in extended family and whenever a baby was born in the family (my younger sibling/cousin), I always liked them, playing with them. So when this new cousin was born when I was 9 years old, I was really excited to see her. When I saw her, I felt she was "ugly" and her cheeks looked fat to me (I am describing exactly as I felt as a 9 year old so using the language). I pretended to like her and played with her bur never really felt affection and always found her face to be weird (again, I found it weird as a child and describing what I felt then, now when at her childhood photos, she was really a cute baby and child). Because I never really felt affection for her as a child, I wasn't really close to her after our early teens. Though all the cousins drifted apart as we grew older, but she always felt odd.

And recently I heard my mother talking on the phone to someone in the family and it turned out that she was adopted as a baby. We were never told about that. But after hearing that, everything I felt as a child came rushing back to me. I am trying to pinpoint what exactly I found odd about her and her appearance but can't place a finger. When I compare her appearance to other female cousins, I can't really think of something specific which is different. But it is just that all the other cousins felt like "family" and she didn't.

Has anyone had such experience personally or heard about something similar from others, or read about this. Do we have more powerful senses as children, like can we smell something which we can't when we grow up? Why exactly I felt like that?

(She is married and is a mother and I am almost 40).