Is a 17 year old sister slow dancing on her brothers feet (my husband who is 22) with her arms around his neck weird or normal sibling behavior?

She is always trying to hold his hand and put her face in his face and touching foreheads together and trying to cuddle him and she is 17 years old and drapes all over my husband like he is her property and it makes me uncomfortable. Now i caught them slow dancing to no music and they were holding each other like we did on our wedding night and she was dancing on his feet and I’m very weirded out. She isn’t a little girl anymore and I feel it’s weird behavior but I’d like other ppls opinions
Is a 17 year old sister slow dancing on her brothers feet (my husband who is 22) with her arms around his neck weird or normal sibling behavior?
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