Opening up To others as an only child?

I hear it all the time “you must be an only child” 🤔 and never understand what that means. Or having the only child syndrome whatever there are times where my social battery dies, and I have to recharge.
I like to think I’m an extroverted introverted person. I am a Leo August not that that matters. But in order for me to one day, Marry hopefully a big family, or have others in my life, I would like to have room and space for another person or people I would like to do better with open up more but I really don’t know how I go out I’m not afraid to eat alone I’m not afraid to do certain things by myself with caution and safety, but what does it mean when people talk about being an only child? Does it prohibit me from doing things or understanding people?
Opening up To others as an only child?
Opening up To others as an only child?
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